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CYAN AMID 



Manufacture, Chemistry and Uses 



BY 



EDWARD J. PRANKE, B.Sc. 



1913 

THE CHEMICAL PUBLISHING COMPANY 

EASTON, PA. 



LONDON, ENGLAND : 
WILLIAMS & NORGATE 

14 HENRIETTA STREET, CONVENT GARDEN, W. C. 






Copyright, 1913, by Edward Hart. 



(CI.A34 78 61 



PREFACE. 

This volume is intended to be a review of the present knowl- 
edge of Cyanamid, particularly its chemical and agricultural 
properties. Its purpose is to render some assistance to the 
investigator who has neither the time nor the library facilities 
to enable him to make a thorough study, yet who wishes to 
broaden his knowledge of Cyanamid. Most of the important 
literature on this subject is written in foreign languages, and 
many valuable papers occur in journals not found in the ordi- 
nary agricultural or chemical library. Moreover, the opinions 
that have been expressed on almost every phase of the be- 
havior of Cyanamid are so diversified and frequently so deeply 
buried in controversy that the casual reader is at a loss to 
know what to accept as generally established facts. It is hoped 
that the present volume will give to the reader a consistent ex- 
planation of Cyanamid that will form the starting point for the 
acquisition of further knowledge. 

In order to arrive at an understanding of the principles 
underlying particular phenomena it is necessary to adopt at the 
beginning of an investigation some sort of working hypothesis 
that will account for the observed facts. Every further fact 
that is acquired must then verify the original hypothesis or the 
latter must be modified to fit the facts. The constant re- 
modeling of ideas to agree with observed facts finally leads to a 
system of knowledge, in which every fact explains to a cer- 
tain extent every other fact, and in no case contradicts any of 
them. Such a system of knowledge of Cyanamid, it is be- 
lieved, is now at hand. The pure chemistry of Cyanamid, its 
physico-chemical action in the soil, its biological behavior, and 
its agricultural properties, as presented in this volume, are con- 
sistent with each other. Such consistency is believed to induce 
confidence in the validity of the views expressed. Further 
experiments may make necessary some slight changes, but the 
general scheme of the properties of Cyanamid may now be con- 
sidered as quite definitely established. 



iv PREFACE 

There is no question but that Cyanamid will play an import- 
ant part in the future development of agriculture, and that a 
great deal of research will be undertaken to broaden the knowl- 
edge of its practical application. Much labor has been wasted 
in the past by the pursuance of faulty methods, and a great 
deal of work has been but the duplication of earlier efforts, 
and has contributed little that was not known before. If the 
publishing of this book will direct research into the fields that 
still remain more or less unexplored, and if it is helpful in 
avoiding the errors of past investigations, its purpose will have 
been accomplished. 

Nashville, Tenn. 
January, 1913. 



TABLE OF CONTENTS. 



Preface lu 

CHAPTER I. Discovery and Manufacture of Cyanamid-. i 

History of Technical Process I 

Nomenclature of Cyanamid Industry 3 

Manufacture of Commercial Cyanamid 4 

Preparation for Use as a Fertilizer 7 

Commercial Derivatives 8 

CHAPTER II. Preparation and Properties of Cyanamide io 

Preparation I o 

Properties T i 

Action of Heat 1 1 

Action of Acids 12 

Action of Alkalies 12 

Action of Oxidizing and Reducing Agents 13 

Other Reactions 13 

Metal Salts 13 

Dimetal Salts 13 

Calcium Cyanamide 14 

Acid Calcium Cyanamide 14 

Basic Calcium Cyanamide 16 

Calcium Cyanamide Carbonate 16 

Silver Cyanamide 17 

DICYANDIAMIDE 17 

Dicyandiamidine 18 

CHAPTER HI. Analytical Methods 19 

Determination of Total Nitrogen 19 

Determination of Cyanamide and Dicyandiamide 20 

Caro Method 20 

Brioux's Modified Caro Method 21 

Determination of Urea 22 

Identification of Amidodicyanic Acid 23 

Identification of Ammeline 23 

CHAPTER IV. Storage of Cyanamid 24 

Factory Test on Large Scale 24 

Test of Two Bags 25 

Chemical Changes in Storage 28 

Relative Amounts of Decomposition Products 29 

CHAPTER V. Decomposition of Cyanamid in the Soie 32 

Factors Involved 32 

Experiments of Ulpiani 32 

Experiments of Kappen 34 

First Stage of Decomposition 37 

Second and Third Stages of Decomposition 38 

Influence of Concentration 40 

Influence of Temperature 43 

Influence of Soil at ioo°C 43 



vi TABLE OF CONTENTS 

PAGE 

Nature of Products formed in Soil at Ordinary Temperatures- 44 

Effect of Changing Ratio of Liquid to Soil 46 

Influence of Aeration 47 

Influence of Electrolytes 48 

Nature of Effective Soil Constituents 48 

Effect of Zeolites 49 

Effect of Carbon 50 

Experiments with Natural Colloids 51 

Experiment with Sterilized Soil 5 b 

Conclusions 57 

CHAPTER VI. Retention of Cyanamid Nitrogen in Soil- 60 

CHAPTER VII. Nitrification of Cyanamid Nitrogen 62 

CHAPTER VIII. Toxicity of Fertilizers 65 

Meaning of ' ' Poison " 65 

Conclusions of Dr. Paul Wagner 66 

Other Explanations of Toxic Action 73 

Dicyandiamide 74 

Formation 75 

Decomposition 75 

Conversion in Soil 77 

Pure Substances and Toxicity 80 

Conclusion 82 

CHAPTER IX. Agricultural Use of Cyanamid 83 

Fertilizer Tests 83 

Use as a Weed Destroyer 86 

Directions for Application as Fertilizer 87 

Use of Complete Fertilizer Mixtures 89 

CHAPTER X. Making Fertilizer Mixtures With Cyanamid 90 

Mixtures with Ammonium Salts 90 

Mixtures with Acid Phosphate 91 

Other Mixtures 93 

Advantages of Cyanamid in Fertilizer Mixtures 93 

Drying Action 93 

Preventing Loss of Nitric Nitrogen 93 

Preventing Bag-rotting 94 

CHAPTER XI. Permanganate Availability of Cyanamid.. 95 

Solubility on Filter 95 

Solubility in Flasks 96 

Rate of Solution in Flasks 96 

Neutral Permanganate Method 96 

Alkaline Permanganate Method 97 

Modified Alkaline Permanganate Method 98 

CHAPTER XII. Fire and Water Hazard of Cyanamid 102 

Test for Flammable Gases 102 

Spontaneous Heating Tests 102 

Test with Water 103 

Acid Tests 103 

Behavior of Product when Heated 104 

Test with the Oil Used 104 

General Behavior when Treated with Water 105 



CHAPTER I. 



Discovery and Manufacture of Cyanamid. 



The problem of the artificial fixation of atmospheric nitro- 
gen has engaged the attention of scientists for the greater part 
of a century. The rapid growth of the fertilizer industry that 
has attended the development of agricultural science, and the 
great increase in the number and extent of chemical industries, 
during the past fifty years, have emphasized the necessity for 
artificial methods of maintaining and increasing the world's 
stock of combined nitrogen. One of the influences that stim- 
ulated immediate action was the introduction in 1887 by 
MacArthur and Forest, and at about the same time independ- 
ently by Siemens & Halske, of Berlin, of the cyanide process 
for leaching gold and silver from their ores. This discovery 
produced a strong demand for cyanides, which had hitherto 
been used to the extent of only a few hundred tons a year, 
principally in the dye-industry and to a smaller extent in 
electroplating. 

Attempts had been made early in the nineteenth century to 
living about the direct synthesis of cyanogen from atmospheric 
nitrogen and carbon. Among other processes, that worked 
out in 1847 by Bunsen and Playfair, in which barium car- 
bonate was heated in an atmosphere of pure nitrogen, seemed 
promising, but did not prove to be commercially successful. 
The introduction of the electric furnace in 1894 by Moissan 
and by Willson, for the production of carbides on a large 
scale, afforded a new instrument for further research. Siemens 
and Halske, among others, at once adopted the use of the elec- 
tric furnace for the working out of the problem of nitrogen fixa- 
tion. In 1895, they worked on the process of Prof. H. Meh- 
ner, which consisted in fusing a mixture of sodium carbonate 
and carbon and conducting nitrogen through the hot mass. In 
the same year they took up the process of Prof. Adolph Frank 
and Dr. Nicodem Caro, which consisted in subjecting a mix- 



2 CYAN AM ID MANUFACTURE, CHEMISTRY AND USES 

ture of barium carbide, sodium hydroxide, potassium hydroxide 
and carbon at a high temperature to the action of steam and 
nitrogen. Frank and Caro, with the co-operation of F. Rothe, 
found in 1895 that dry nitrogen is essential to successful 
absorption. 

In 189S it was found that when barium carbide is heated to 
a temperature of 700 ° to 8oo° C, in the presence of nitrogen, 
about 30 per cent, of the carbide is changed into barium 
cyanide and the remainder into barium cyanamide. The re- 
actions can be represented by the following simple equations : 

BaC 2 + N 2 = Ba (CN)„ 
Ba(CN) 2 = BaCN 2 + C. 

Since it was desired to have all the nitrogen in the form of 
cyanide, further operations were necessary. The product of 
the above reactions was fused with soda, when the carbon 
again reacted with the cyanamide group and produced the 
cyanide form. The cyanide was leached out with water, and 
treated with ferrous carbonate to form the ferrocyanide, which 
was sold as such or fused with sodium to form pure sodium 
cyanide. The barium carbonate residue was again used to 
produce barium carbide, as represented by the reactions : 
BaC0 3 + heat = BaO + C0 2 , 
BaO + 3C = BaC 2 + CO. 
The fall in the price of cyanides due to the interruption in 
the production of gold during the Boer War in South Africa 
made it necessary to seek cheaper methods of manufacture. 
It was found that calcium carbide could be manufactured at 
less cost, and also had the advantage of possessing a lower 
molecular weight. This carbide required a temperature of 
from i,ioo° to 1,200° C. for the absorption of the nitrogen, but 
combined it entirely in the form of calcium cyanamide, without 
the formation of any cyanide. By fusion with alkaline salts, 
however, the cyanamide form, in the presence of carbon, 
readily goes over to the cyanide form, which can be leached 
out with water, if desired, and be further purified. When 
sodium chloride is used as the fluxing agent, the resultant mass 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 3 

contains about 30 per cent, sodium cyanide, and is known as a 
"surrogate." It is suitable for use directly for the extraction 
of gold ores. 

Agricultural experiments with the crude calcium cyanamide 
showed that this material is suitable for use as a nitrogenous 
fertilizer, and patents were issued in 1910 to Dr. Albert R. 
Frank, son of Prof. Adolph Frank, and to Herman Freuden- 
berg, a co-worker of A. R. Frank, protecting the use of 
Cyanamid for this purpose. The basic patent protecting the 
process of manufacture of Cyanamid was issued to Prof. 
Adolph Frank and Dr. Nicodem Caro in 1908. 

The large demands of agriculture for cheap nitrogenous 
fertilizer materials have directed the efforts of the manu- 
facturers toward the production of Cyanamid rather than of 
cyanides and other derivatives. At present, the total output 
of sodium cyanide derived from Cyanamid is only about 2,000 
tons per annum, all made in Germany, while the world's pro- 
duction of Cyanamid is estimated at about 120,000 tons per 
annum. The factory of the American Cyanamid Company, 
at Niagara Falls, Canada, now has a capacity of 30,000 tons 
per annum, and extensions now under way will increase this to 
60,000 tons per annum. There are thirteen Cyanamid factories 
abroad, located in Germany, Italy, France, Switzerland, 
Austria, Norway, Sweden and Japan. 

NOMENCLATURE OF CYANAMID INDUSTRY. 

With the development of the Cyanamid industry there has 
grown up a nomenclature that is often confusing to the un- 
initiated. The terms here defined will be understood to have 
the following meanings throughout this treatise : 

Lime-nitrogen. — Crude calcium cyanamide, ground to a fine 
powder after removal from the ovens in which it is formed. 
It contains about 55 per cent, of calcium cyanamide, CN.NCa, 
about 2 per cent, calcium carbide, and about 20 per cent, of 
free calcium oxide. 



4 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

Cyanamid. — This is a trade name for the completely hydrated 
material prepared for use as a fertilizer in the United States. 
It contains about 45 per cent, calcium cyanamide, 27 per cent, 
calcium hydroxide and no carbide. The name is always 
capitalized and has no final "e." 

Cyanamide. — The compound represented by the formula 
CN.NHo. It is sometimes referred to as acid cyanamide, or 
free cyanamide. 

Calcium Cyanamide. — The chemical compound of the for- 
mula CN.NCa, or CaCN 2 , as it is freqently written. 

Calcium Cyanamid. — The name used by the United States 
Department of Agriculture and by some State Departments of 
Agriculture to designate commercial Cyanamid. It is some- 
times used to indicate the substance represented by the formula 
CN.NCa, but for the sake of clearness the compound CN.NCa 
will be called calcium cyanamide in the present paper. 

Nitrolim. — The trade name for the material sold in England 
for agricultural purposes. It is a lime-nitrogen to which has 
been added just enough water to destroy the carbide. Practi- 
cally all the free lime is present as calcium oxide. 

Kalkstickstoff. — The commercial material manufactured in 
Germany for use as a fertilizer. It is similar to nitrolim. 

Stickstoffkalk. — A crude calcium cyanamide made by nitri- 
fying a calcium carbide which contains about 10 per cent, of cal- 
cium chloride. Its manufacture in Westeregeln, Germany, 
under the Polzeniusz patents was discontinued in 1910. 

Calciocianamide. — The Italian commercial product, com- 
pletely hydrated. 

Cyanamide de calcium. — The French commercial product, 
completely hydrated. 

MANUFACTURE OF COMMERCIAL CYANAMID. 

The first step in the manufacture of Commercial Cyanamid 
is the preparation of calcium carbide. This is brought about 
in the usual manner by fusing in an electric furnace a mixture 
of lime and coke in accordance with the following equation: 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 5 

CaO + 3C — CaC 2 + CO. 

The carbide is removed from the furnace at regular inter- 
vals, is cooled, crushed to a fine powder, and packed in the 
nitrifying ovens. These are cylindrical, perforated steel cans, 
set in heat-insulated brick ovens. A carbon pencil through 
the axis of the can is used to heat the carbide to the combining 
temperature. On admission of the nitrogen to the cans the 
following reaction takes place: 

CaC, + N 2 — CaCN 2 + C. 

This reaction is accompanied by an evolution of heat which 
is just about sufficient to maintain the mass at the combining 
temperature. The commercial calcium carbide used contains 
about 20 per cent, of impurities, which so influence its physical 
and chemical properties that the absorption of nitrogen takes 
place very readily at atmospheric pressure at a temperature of 
about i,ioo° C. The addition of catalytic agents, principally 
haloids, suggested by various investigators, is not necessary for 
the fixation of nitrogen, since the manufacturer can easily 
regulate the reactions by suitable disintegration of materials 
and by other mechanical means. 

Nitrogen is obtained either by fractional distillation of 
liquid air, or by means of the copper oxide process. In the 
latter, air is passed through a red-hot mass of finely divided 
copper, suspended in asbestos or other inert material. The 
copper combines with the oxygen and allows the nitrogen to 
pass through. The copper oxide is easily recovered for use 
by reduction in situ with a suitable gas, such as natural gas. 

The nitrogen used must be pure and dry, otherwise, at high 
temperatures, there is destruction of the carbon pencils, and 
of calcium carbide, according to the following reactions : 

C + O — > CO, 
C + CO, — 2CO, 
C + H 2 0*~ CO + H„ 
H 2 + CaC 2 — * CaO + C 2 H..„ 
3O + CaC 2 — > CaO + 2CO. 



6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

Carbon dioxide also destroys the calcium cyanamide with 
formation of calcium oxide, carbon monoxide and free nitro- 
gen. 

The reaction by which calcium cyanamide is formed is 
reversible: 

CaC 2 + N 2 = CaCN, + C. 

The temperature of reversal at atmospheric pressure varies 
greatly with the composition of the carbide used. Thus the 
temperature of reversal lies at about 1,360° C., 1 for a crude 
calcium cyanamide containing 21.1 per cent, combined nitro- 
gen, and made from a commercial carbide of the following 
composition : 

Per cent. 

CaC 2 82.30 

C 1.20 

CaO 14.72 

CaSi 0.06 

Ca 3 Pj 0.07 

CaS 0.13 

Ferrosilicon 0.72 

Not determined 0.80 

An increase of the free lime in the carbide greatly lowers 
the critical temperature. Thus with a carbide containing 75 
per cent. CaC 2 the equilibrium point lies at about 1150° C. 2 

The effect of nitrogen pressure on the equilibrium point has 
been investigated by M. Thompson, who found that the tem- 
perature at equilibrium varies directly as the pressure. 3 Since 
calcium cyanamide is decidedly volatile at the equilibrium tem- 
perature, even as low as 1,050° C, and distils to the colder 
parts of the apparatus the determination of the equilibrium 
conditions is open to some errors, but these may not be large 
enough to vitiate the general conclusions that have been drawn. 

It is owing to the reversibility of the reaction that nitrogen 

1 Caro, Chem. Trade Jour., 1909, p. 622. 

2 LeBlanc & Eschmann, Zeit. fiir Elek., i9ri, 17, 20-34. 

3 Thompson & Lombard, Met. and Chem., Eng. , 1910, 617, 682. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 7 

cannot be absorbed by liquid carbides as the latter leaves the 
furnace, since calcium cyanamide cannot exist at the tempera- 
ture of liquid carbide. As the carbide cools it becomes practi- 
cally impermeable to gases and absorption takes place only on 
the surface to a slight depth. 

Processes for the nitrifying of a heated mass of lime and 
coke have not been commercially successful. 

The energy consumption for the fixation of one ton of nitro- 
gen as calcium cyanamide is about three horse power years, 
including the manufacture of the carbide and all subsequent 
factory operations. 

PREPARATION FOR USE AS FERTILIZER. 

Cyanamid finds its principal use in agriculture, as a source 
of nitrogenous plant food, and for this reason practically all 
the crude calcium cyanamide is converted into a form more 
suitable for its incorporation in complete fertilizers. To this 
end, water is added to the crude material in a rotating cylinder; 
the one or two per cent, of calcium carbide is decomposed and 
the lime slaked. This powdered Cyanamid is converted to 
granulated Cyanamid as follows : A small amount of water 
is mixed with it, and the damp material is run through brick 
presses. The resulting bricks harden rapidly, and are stored 
until the material is to be shipped, when they are run through 
a series of crushing rolls and screens. The coarse material, 
which passes through a 15-mesh standard screen and over a 
60-mesh standard screen, is practically free from dust, and 
is known commercially as Granulated Cyanamid. The fine 
material, mostly smaller than 60-mesh, is either incorporated 
with fresh powdered Cyanamid and again run through the 
brick presses, or it is mixed with several per cent of an odor- 
less oil to reduce the dustiness, and is sold without further 
treatment. Both grades of Cyanamid are packed in ordinary 
fertilizer bags, and are distributed in carload lots to manu- 
facturers of mixed fertilizers. Material so prepared contains 
nitrogen equivalent to 18 to 20 per cent, of ammonia, and is 
2 



b CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

sold on the basis of its nitrogen content, as determined by 
analysis. 

The following is a typical analysis of commercial Cyanamid. 

Per cer.t. 

Calcium cyanamide CaCN 2 45-92 

Calcium carbonate CaCO s 4.04 

Calcium sulphide CaS 1 .73 

Calcium phosphide Ca 3 P 2 0.04 

Calcium oxide, free CaO — 

Calcium carbide CaC 2 

Calcium hydroxide Ca(OH) 2 26.60 

Free carbon C 13. 14 

Iron and alumina R 2 3 1.98 

Silica Si0 2 1.62 

Magnesia MgO o. 15 

Combined moisture — 3.12 

Free moisture H,0 0.35 

Undetermined — 1.31 

100.00 

COMMERCIAL DERIVATIVES. 

Ammonia. — Steam, at a high temperature and pressure, con- 
verts calcium cyanamide quantitatively into calcium hydroxide 
and ammonia, thus forming a convenient source of ammonia 
for the manufacture of ammonium salts. The carbon, which 
is in the form of graphite, and the lime, can be used over again 
for the production of carbide. 

Nitric Acid. — By the Ostwald process, ammonia can be oxi- 
dized to nitric acid, mixtures of thoria and ceria being used as 
catalyzers. No external supply of energy is required in this 
process. 

Cyanides. — When calcium cyanamide and carbon are fused 
together with alkaline salts, in the absence of carbide the cal- 
cium cyanamide is converted into calcium cyanide: 

CaCN 2 + C — Ca(CN) 2 . 
The product of this reaction is called a "surrogate." It is used 
in the recovery of metals by the cyanide process. 

The above reaction is completely reversed in the presence 
of carbides, hence their absence is imperative in this process. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 9 

Dicyandiamide. — This derivative is easily prepared by leach- 
ing the crude calcium cyanamide mass with hot water, pre- 
cipitating the lime in the filtrate with carbon dioxide, and con- 
centrating the filtrate. Dicyandiamide is used in the dye in- 
dustry, and also as a deterrent in nitro-explosives, in place of 
ammonium oxalate. 

Other derivatives, such as urea, guanidine, nitro-guanidine, 
are being made at the Spandau works, in Germany. A process 
has also been worked out for the production of synthetic indigo 
by the action of dialkylcyanamides on Phenylgycine and its 
derivatives. 

Ferrodur and intensit are special mixtures prepared for 
metallurgical purposes. Ferrodur is a cementing powder used 
in place of potassium cyanide for hardening iron and steel in 
ovens. Intensit is a hardening powder for hardening iron and 
steel in open fires ; it is used in place of potassium ferro- 
cyanide. There are other powders of a similar nature with 
special names differing only in the proportion of active in- 
gredients that they contain. These products are of consider- 
able importance to metallurgy, since they are cheap, yet 
efficient for the purposes for which they are sold. 



CHAPTER II. 



Preparation and Properties of Cyanamide. 



PREPARATION. 

Free cyanamide, CN.NH 2 , was first obtained by Bineau, in 
1838, by the action of ammonia on chlorcyan, but it was not 
isolated by him from the ammonium chloride with which it 
was formed. The Italian chemists Cloez and Cannizzaro, 1 in 
185 1, effected the separation, and gave the first description of 
the compound. 

Their method consists in passing chlorcyan into a solution 
of ammonia in absolute ether, filtering off the crystalline am- 
monium chloride and evaporating the solution in vacuo below 
40 . The reaction takes place according to the following 
equation : 

2NH, + CNC1 — * CNC1 2 NH 4 + NH. 

It can also be prepared by the action of freshly precipitated 
mercuric oxide on thio-urea, in the presence of a little am- 
monium thiocyanate, which dissolves some of the mercuric 
oxide as the double thiocyanate, and so renders it more active : 
NH 2 NH 2 

S:C/ "~ C \ + H ' S 

NH 2 N 

It is most conveniently prepared from either commercial 
sodium cyanamide or commercial calcium cyanamide. 

From Commercial Sodium Cyanamide. 2 — Twenty-five grams 
of the salt are gradually added to 37 grams of hydrochloric 
acid (sp. gr. 1.19) with strong cooling, and the water is re- 
moved by distillation in vacuo below 40 C. The residue 
solidifies on cooling; it is extracted with ether, the ether dis- 
tilled off from the solution, and the cyanamide caused to 

1 Compt. rend., XXXII, 62. A, 78, 229, and Leibig's Annalen 78, 229. 

2 Caro, Schiick, Jacoby, Zeit Angew Chem. 1910, XXIII, 2405, 2417. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES II 

crystallize by cooling. It is purified by recrystallization from 
ether. Yield about 5 grams. 

From Commercial Calcium Cyanamide. — Fresh commercial 
Cyanamid or better, the unhydrated lime-nitrogen, is extracted 
with cold water (solubility about 0.9 grams nitrogen in 100 cc. 
water). The calcium is removed either with oxalic acid or 
aluminium sulphate, but preferably with the latter. After re- 
moval of the calcium sulphate and alumina by filtration, the 
filtrate is evaporated in vacuo below 40 , and the residue ex- 
tracted with ether. It can be purified by recrystallization from 
ether. 

PROPERTIES OF CYANAMIDE. 

Cyanamide, 1 CN.NH,, most probably has the formula 

,NH, 
C <^ , although in a very few reactions it seems to act as 

if it were carbodiimide, Cx" . It is a colorless, crystal- 

line solid, which melts at 41-42 C, as usually prepared. It 
can be undercooled to 12 without solidifying. On stirring 
with a sharp-pointed glass rod the undercooled liquid freezes. 
The carefully purified substance melts sharply at 46 C. 2 It 
is easily soluble in water, alcohol and ether, and is volatile in 
steam. It is slightly soluble in carbon disulphide, chloroform 
and benzol. 

Action of Heat. — Pure cyanamide is perfectly stable at ordi- 
nary temperatures, but polymerizes slowly on heating above 
its melting point. Impure cyanamide polymerizes slowly at 
ordinary temperatures. The principal polymer is dicyandia- 

/NH. 
mide, NH: C<( >CN, or (H 2 CN 2 ) 2 , which is probably 

X NH X 

cyan-guanidine. By strong heating, other derivatives are 

1 Sidgwick, Organic Chemistry of Nitrogen, p. 216, (Oxford, 1910). 
- G. Henschel, Diss. Univ. of Leipzig, 1912. 



12 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

formed, the most important of which are, the polymer 

N 

//\ 
Tricyantriamide or Melamine H,N — C C — NH.„ and Me- 

I II 

N N 

%/ 

C 

NH 3 
lam, C 6 H,N n , and Mellon, C 6 H 3 N a . Ammonia is evolved 
during the formation of these bodies. By the action of super- 
heated steam the conversion of cyanamide to ammonia is 
almost quantitative. 

Action of Acids. 1 — Cyanamide reacts readily with acids ; with 
nitric acid forming urea nitrate (95 per cent, conversion) ; 
with sulphuric acid and phosphoric acid giving mostly urea, 
(about 95 per cent, conversion) together with some ammeline, 
C 3 N 3 (NH 2 ) 2 OH; ammelide, C 3 N 3 (NH 2 ) (OH) 2 ; possibly 
cyanuric acid, C 3 N n (OH) 3 , and some ammonia. 

Cyanamide combines directly with the haloid acids. It com- 
bines slowly with free H 2 S, readily with yellow ammonium 
sulphide, with formation of thio-urea. Thio-urea is also 
formed by the action of thioacetic acid on cyanamide in 
alcoholic solution. Acetic acid produces principally ammo- 
nium acetate (about 80 per cent, conversion) and some urea. 

Action of Alkalies. 2 — The strong alkalies KOH or NaOH 
in aqueous solutions produce almost entirely urea, with no 
trace of dicyandiamide ; weak alkalies, NH 4 OH or MgO, pro- 
duce dicyandiamide almost exclusively at first, and then 
ammonia. CaO, however, produces a mixture of urea, dicyan- 

diamide, ammeline, amidodicyanic acid I O : Q.C ) ,. 

v X NH - CN 7 

ammonia and other bodies. 

1 Ulpiani, Gas Chim., Ital. II, No. 4, 358-417. 

2 Beilstein's Handbuch der Organische Chemie. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 1 3 

Hence, with strong acids and strong bases, cyanamide in 
aqueous solutions forms principally urea ; with weak acids 
principally ammonium salts; with weak bases dicyandiamide, 
which decomposes further to ammonia; with lime, a mixture 
of urea, dicyandiamide and other derivatives. 

Action of Oxidizing and Reducing Agents. — In the chapter 
on availability it will be shown that oxidizing agents convert 
the nitrogen of cyanamide or its derivatives into forms more 
insoluble in water and less easily decomposed by strong 
alkalies. 

By the action of zinc and hydrochloric acid, cyanamide yields 
ammonia and methylamine : 

CN. NH 2 + H 2 •— CNH -f NH. P 
CNH + 2H, — CH 3 ,NH r 

On heating with potassium nitrite solution a violent reaction 
takes place, and C0 2 , N 2 and dicyandiamide are produced : 
4 CN.NH 2 + 4 KN0 2 — * 2K 2 C0 3 + 4 N 2 + (CN.NH 2 ) 2 + 2 H 2 0. 

Other Reactions. 1 — In cyanamide, either one or both of the 
hydrogen atoms can be displaced by metals, alkyl or aryl 
groups, or by alcohol or acid radicals. It combines with 
amino-acids, especially in the presence of ammonia. It com- 
bines with ammonium chloride at high temperatures, forming 
guanidine hydrochloride. Heated with ammonium sulphide 
it yields guanidine hydrosulphide. It combines directly with 
cyanogen to form a yellow, amorphous powder. With potas- 
sium cyanate it forms potassium amidodicyanate, K.C 2 H 2 N 3 0. 
It combines directly with chloral, and also with aldehydes, but 
with the separation of water. 

Metal Salts. — The dimetal salts of the alkali metals can be 
prepared only in the dry way, since in aqueous solution they 
lose one of the metal ions by hydrolysis. Thus, Na 2 CN 2 in 
aqueous solution yields NaHCN 2 : 

Na 2 CN 2 + H 2 = NaHCN 2 + NaOH 
1 Beilstein, Handbuch der Org. Chem. 



14 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

Na 2 CN 2 on fusion with carbon yields sodium cyanide: 
Na 2 CN, + C <~ 2NaCN. 

,NCa 
Calcium Cyanamide, CaCN 3 or C^ , can be made by the 

fusion of calcium cyanate: 1 

Ca (CNO) 2 — CaCN 2 + C0 2 

or by fusion of cyanamide or its polymers with calcium oxide. 
Calcium cyanamide forms colorless crystals which sublime 
at about 1,090° C. at atmospheric pressure. It is insoluble in 
alcohol, but easily soluble in water (about 2.5 g. in 100 cc. 
water at 25° C). Upon solution of the calcium cyanamide in 
water it is directly hydrolyzed into the acid calcium cyanamide 
and calcium hydroxide. 

2 CaCN, + 2 H,0 — Ca(CN.NH) 2 + Ca(OH) 2 . 

That such hydrolysis takes place as indicated by the equa- 
tion is shown by the relative amounts of lime and nitrogen 
existing in solutions of calcium cyanamide. C. Ulpiani 1 inves- 
tigated the relation of lime to nitrogen in a solution of calcium 
cyanamide kept at a constant temperature for several weeks. 
At intervals of several days determinations were made of 
total nitrogen, nitrogen in the form of cyanamide, and calcium 
in solution. It was noted that crystals of pure calcium 
hydroxide, as determined by analysis, were deposited on the 
walls of the vessel after a day or two. The quantities of 
lime and nitrogen found in the solution are shown in Fig. 1. 

Since the solubility of calcium cyanamide is much greater 
than that of calcium hydroxide, a concentrated solution of 
calcium cyanamide is, after hydrolysis, saturated with respect 
to calcium hydroxide. In addition, there is present lime as 
a calcium compound of cyanamide. If this compound is cal- 
cium acid cyanamide, Ca(CN.NH)._,, there will be in solution 
one atom of calcium to four of nitrogen, or 56 parts by weight 

1 Beilstein loc cit. 

2 Rend. Soc. Chim. di Roma, n. 4 (1906). 



CYANAMID MANUFACTURE, CHEMISTRY AND USES 15 

of CaO to 56 of N, or equal weights of each. By reference 
to the curves in Fig. i it is seen that if the ordinate represent- 
ing the amount of CaO present as Ca(OH) 2 is subtracted 
from the ordinate of total CaO, the ordinate of CaO combined 
in other forms (with cyanamide) would coincide with the 
ordinate of nitrogen present as cyanamide; that is, the amounts 
of CaO and N present are in the relation demanded by the 
formula Ca(CN.NH) 2 . 

On long standing of the solution, the acid salt Ca(CN.NH) 2 
decomposes, forming principally urea, some dicyandiamide, 



«5 




D-Total^ 




OaO- Total 




H- aa 




Cyanamide 








t* 


N \ 
N \ 


.«« 


\ \ 


< 


N \ 


a 


\ \ 


< 


\ \ 


3 


\ \ 




\ \ 




\ \ Temp. 35°C 
\ V 




\ ^\ 


4. 






V ^^ 


1 


^^ . 


w 
&* 


""-•s. 


** >^ 


CaO- as 


~~ ----__ 


0a(0H) 2 


"""" — — —. 


«a 




c 


4 & 12 16 ZO Z4 



Days 

Fig. I.— Variation of nitrogen and calcium in a solution of lime-nitrogen. 

and small quantities of melamine, amidodicyanic acid and 
ammonia. The dicyandiamide diminishes slowly, and finally 
probably disappears entirely. This is shown in the following 
analyses by G. Liberi 1 of a solution made by extracting lime- 
nitrogen containing 18.63 P er cent, cyanamide nitrogen, with 
twenty times its weight of cold water. The nitrogen figures 
are given as a percentage of the dry lime-nitrogen. 

1 Ann. R. Staz. Chim. Agrar. Sper di Roma., 191 1, Vol. V, Series II. 



l6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

Nitrogen in solution 

As cyanamide As dicyanamide 

After Per cent. Per cent. 

I day 1456 0.70 

3 days 11.76 1.54 

6 days 9.10 2.84 

11 days 5.18 2.24 

18 days 1.75 1. 71 

31 days 0.00 1.25 

45 days 0.00 0.84 

58 days 0.00 0.53 

76 days 0.00 0.23 

Basic calcium cyanamide is formed in solutions containing 
an excess of lime: 

N N 

/// /// 

C v + Ca(OH) 2 — * C v /CaOH 

X NCa X N< 

^CaOH 

It can be obtained from lime-nitrogen by extracting with a 
small portion of water, filtering, and allowing the solution to 
stand several hours. Long, needle-shaped white to trans- 
parent crystals separate out on the walls of the vessel. Filter 
with suction in the absence of carbon dioxide (under a bell- 
jar). Dry under a bell-jar over caustic potash. 

This salt is almost insoluble in water. In the dry condition 
it is stable at ordinary temperatures, but when heated to 
120 C. it rapidly decomposes to dicyandiamide and calcium 
hydroxide. 

Calcium cyanamide carbonate 1 is readily formed by the 
action of carbon dioxide on calcium cyanamide in the presence 
of moisture. It can be prepared by extracting lime-nitrogen 
with one and one-half times its weight of water, filtering and 
bubbling CO, through the filtrate. In about half an hour a 
white precipitate forms, which can be filtered and washed with 
alcohol or ether. 
1 Ulpiani, loc cit. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES \"J 

N 

/// 
CaCN 2 + C0 2 + H 2 — * C x ,Ca 

X N< | 5 H 2 0. 
X C0 2 

Calcium cyanamide carbonate is somewhat insoluble in water, 
and insoluble in alcohol and ether. On standing in dry air 
it slowly loses 4 molecules of water of crystallization, and at 
the same time decomposes to dicyandiamide and calcium car- 
bonate. The same change takes place rapidly when heated : 
N 

/// 
2C V /Ca.5H.,0 — * (CN.NH,) 2 + 2 CaC0 3 + 8H 2 

X C0 2 

Silver Cyanamide, C N.N Ago. — Obtained on treating an 
ammoniacal solution containing cyanamide with very dilute 
(1 : 150) solution of silver nitrate. 1 More concentrated solu- 
tions yield a mixture of this salt and double or basic silver 
salts, containing, however, all the cyanamide. 

Silver cyanamide is an amorphous, yellow substance, almost 
insoluble in dilute ammonia or caustic potash at ordinary tem- 
peratures, soluble in hot ammonia solutions, easily soluble in 
dilute nitric acid. It is easily soluble in alkali cyanide solution, 
but if an excess of silver nitrate is added, a white, crystalline 
double salt of silver cyanide and silver cyanamide is precipi- 
tated. 

When potassium hydroxide is added to a cyanamide solution 
containing silver nitrate in excess an insoluble mixed precipi- 
tate of silver cyanamide and brown silver oxide is formed, 
which contains all the cyanamide nitrogen. 

.NH 2 
Dicyandiamide," NH:C( .—Obtained by extract- 

X NH.CN 

ing lime-nitrogen with boiling water, concentrating the solu- 

1 Caro, Schiick, Jacoby, loc cit. 

2 Beilstein, loc cit. 



l8 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

tion to a syrup and allowing to crystallize. It forms trimetric 
plates or thin leaves, melting at 205 C. It is decomposed by 
heating, with evolution of ammonia and formation of mela- 
mine, melam, and other derivatives. Dicyandiamide is some- 
what easily soluble in water and alcohol, but almost insoluble 
in ether. It combines with ammonium chloride at 150 , giving 
diguanide hydrochloride, C 2 H 7 N 5 HC1; with HC1 at 150 gives 
guanidine hydrochloride, CH 5 N 3 HC1 ; on boiling with baryta 
it gives amidodicyanic acid and ammonia ; with zinc and HC1 
yields methylamine and ammonia ; with H 2 S it gives guanyl- 
thiourea; on heating with urea or cyanuric acid it forms 
ammelin, C a H;;N 5 0, and ammonia. 

Treated with weak or strong acids, or with strong 
alkalies, dicyandiamide goes over to dicyandiamidine, 

/NH 2 
NH : C<^ , caustic crystals, easily soluble in 

^NH.CO.NH, 

water and alcohol. 

Dicyandiamide, treated with silver nitrate solution, forms 
additional compounds containing, according to the conditions, 
one, two and three molecules respectively, of dicyandiamide 
per molecule of silver nitrate. Cold caustic potash added to 
a dicyandiamide solution containing sufficient silver nitrate 
causes a white to brown mixture of precipitates of silver 
dicyandiamide and silver oxide. Silver dicyandiamide is 
slightly soluble in water, easily soluble in ammonia, soluble in 
hot nitric acid ; on prolonged boiling with caustic potash is 
converted into silver cyanamide, CN.NAg 2 , and cyanamide, 
which polymerizes again to dicyandiamide. 

If silver nitrate, then nitric acid, is added to a solution of 
dicyandiamide, a white precipitate is formed, insoluble in 
cold, soluble in hot nitric acid or in excess of ammonia. (Iden- 
tification in mixtures of cyanamide and dicyandiamide. Cyan- 
amide, it will be remembered, gives a yellow precipitate with 
dilute silver nitrate, soluble in nitric acid, but insoluble in 
ammonia.) 



CHAPTER III. 



Analytical Methods. 



DETERMINATION OF TOTAL NITROGEN IN CYANAMID. 

Practically all the Cyanamid manufactured in this country 
prior to January I, 1912, contained about 23 per cent, of its 
total nitrogen in the form of nitrates. Hence, for the deter- 
mination of total nitrogen in such Cyanamid it is necessary to 
use a method that will determine nitrate nitrogen as well as 
nitrogen derived from Cyanamid. For this purpose the Official 
Gunning method, modified for nitrates, is suitable. The 
period of digestion should be at least five hours. The influ- 
ence of the period of digestion is shown in the following values 
obtained on a sample of Cyanamid containing nitrates : 

Per cent, nitrogen 

2 hours digestion 15.61 

3 " " I5-76 

4 " " 16.03 

5 " " 16.06 

All the Cyanamid manufactured in this country since Jan- 
uary 1, 1912, is free of nitrates, and therefore, the simple 
Kjeldahl or Gunning method may be used. The Gunning, 
which is in general use, is carried out as follows: 

REAGENTS REQUIRED. 

N/2 (Half-normal) Sulphuric or hydrochloric acid. 

N/10 (Tenth-normal) Sodium hydroxide, or ammonium 

hydroxide. 
Sulphuric acid, C. P., specific gravity 1.84. 
Sodium hydroxide, saturated solution. 
Potassium sulphate, C. P. 
Cochineal indicator. 

To determine nitrogen weigh out 0.7 gram of finely ground 
sample. Each cc. of half-normal acid is equivalent to 1 per 



20 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

cent, nitrogen. To determine ammonia weigh out 0.85 gram 
of finely ground sample. Each cc. of half-normal acid is 
equivalent to 1 per cent, ammonia. 

Procedure. — Place the carefully weighed sample in a Kjeldahl 
flask of about 300 cc. capacity. Add 10 grams of ground 
potassium sulphate. Shake until well mixed with the sample. 
Add 25 to 30 cc. of concentrated sulphuric acid and shake 
until well mixed. Heat slowly for 30 minutes, then heat with 
a full flame for one and one-half hours. Cool, dilute, and 
transfer to a distillation flask. (Distillation can be made from 
the digestion flask if desired.) Add an excess of sodium 
hydroxide, and distil 200 cc. into a measured quantity of the 
standard half-normal acid, containing some cochineal indi- 
cator. Titrate the excess of acid with tenth-normal alkali. 

DETERMINATION OF CYANAMIDE AND 
DICYANDIAMIDE. 

Caro Method.— Of the various methods for determining 
cyanamide and dicyandiamide, that of Caro 1 seems to be the 
best. The reagents used are as follows : 

(a) Silver acetate solution. 100 grams of silver acetate are 
placed in a liter flask, covered with 400 cc. of 10 per cent, 
ammonium hydroxide, and the flask is filled to the mark with 
water. 

(b) 10 per cent, solution of potassium hydroxide. 

The procedure is as follows : 5 g. of Cyanamid or lime- 
nitrogen is agitated by hand or in a shaking machine with 
450 cc. of water for about 2V 2 hours, and the flask filled to 
500 cc. An aliquot part (250 cc.) is treated with ammonia 
until it smells strongly thereof and then with silver acetate 
solution in excess. The precipitate of silver cyanamide salts 
(p. 12), after shaking and standing a little while, is gathered 
on a nitrogen-free filter, washed with water until no ammo- 
nium salts run through, and the nitrogen in it is determined 
by the Kjeldahl method. 

1 Caro, Schiick, Jacob y — loc cit. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 21 

An aliquot part of the filtrate, now free from cyanamide, 
is treated with potassium hydroxide solution in excess, and is 
boiled until no more ammonia comes off. The precipitate con- 
tains all the dicyandiamide and some silver oxide. Dilute the 
solution with an equal volume of water, filter on a nitrogen- 
free filter, wash with some water, and determine nitrogen in 
the precipitate by the Kjeldahl method. 

Brioux 1 claims that the boiling of the strongly alkaline 
cyanamide-free solution containing the precipitate of silver 
dicyandiamide and silver oxide causes a conversion of about 
1.5 per cent, of the total nitrogen of the dicyandiamide, and he 
has modified the method so as to obviate this error. His 
method is briefly as follows : 

Brioux's Modified Caro Method. — Extract the soluble nitro- 
gen from 1 or 2 grams of finely ground sample by frequent 
shaking for three or four hours in a flask with 250 cc. cold 
water, and filter through a dry filter without washing. In 
one aliquot portion of 100 cc. of the filtrate determine cyana- 
mide and dicyandiamide, and in the other determine cyanamide 
alone. 

For combined cyanamide and dicyandiamide nitrogen : For 
each 0.1 gram nitrogen (approx.) in the solution add 20 cc. 
of 5 per cent, silver nitrate solution. Then add 20 cc. of 
10 per cent, potassium hydroxide solution. A brown precipi- 
tate of mixed cyanamide and dicyandiamide salts forms. 
Filter and wash with cold distiled water. Determine total 
nitrogen in the residue by the Kjeldahl process, substituting 
1 gram copper sulphate in place of the mercury. 

For cyanamide nitrogen : In the other portion of the extract 
from the sample add for each 0.1 gram nitrogen, 20 cc. of 
5 per cent, silver nitrate solution. Add an excess of ammonia. 
A yellowish-brown precipitate forms. Filter and wash with 
water slightly ammoniacal, finishing with cold distilled water 
until the washings are free from soluble silver salts. Dissolve 
the residue in dilute nitric acid (1:2) and determine silver 
1 Annales de la Science agron. francaise et etrangere, April 1910. 



22 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

by the sulphocyanate or other convenient method. One atom 
of silver corresponds to one atom of nitrogen. 

In both the Caro and Brioux methods, however, from 25 to 
30 per cent, of the urea present is precipitated in caustic potash 
solution as silver salts along with the dicyandiamide. 1 Since 
Cyanamid frequently contains more urea than dicyandiamide 
this occasions considerable error. Henschel 2 found that by the 
Caro method about 7 per cent, of the nitrogen as dicyandiamide 
was converted to other forms, presumably by the action of the 
hot caustic alkali in boiling off the the ammonia. The total 
nitrogen was not diminished, hence the urea (?) nitrogen was 
increased at the expense of the dicyandiamide. 

Determination of Urea.— Caro determines the total nitrogen 
remaining in the filtrate from the dicyandiamide separation and 
designates it as urea. Since, however, some of the urea is 
precipitated along with the dicyandiamide and since the nitrate 
may also contain other derivatives, the method can hardly be 
considered as satisfactory. Caro also recommends Liebig's 
titration method for the determination of the urea in the 
filtrate. Ulpiani, 3 however, claims that the mercuric nitrate 
used for the precipitation of urea in this method, also pre- 
cipitates cyanamide and dicyandiamide, if present, dicyandia- 
midine. amidodicyanic acid, ammonia, ammonium salts, and 
probably all nitrogen compounds found in lime-nitrogen. 
Ulpiani suggests the direct solution of the sample of lime- 
nitrogen or Cyanamid with alcohol, but since dicyandiamide as 
well as urea is soluble in alcohol, this procedure would not 
simplify the problem very much. 

The question of analysis of cyanamide derivatives is much 
in need of scientific study, but for the present it will be 
sufficient for most purposes to determine total nitrogen in a 
given sample of Cyanamid, then to determine cyanamide and 

1 Brioux, loc. cit. 

2 Georg Henschel, Das Verhaltendes technischen Calciumcvanamides 

bei der Aufbewahrung sowie unter dem Einfluss von Kulturboden 
und Kolloiden — Diss. Univ. Leipzig. 1912. 

3 Ulpiani, loc. cit. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 21, 

dicyandiamide by the Caro method, and to consider the differ- 
ence as being equivalent to the original urea. The other 
derivatives usually occur in such small quantities that they are 
practically negligible. 

IDENTIFICATION OF AMIDODICYANIC ACID. 

The following is based upon the procedure given by Ulpiani 1 
for the identification of amidodicyanic acid. 

Remove the cyanamide and dicyandiamide (Brioux's 
method), carefully neutralize the filtrate with sulphuric acid, 
and treat with copper sulphate. In a day or two greenish 
crystals of copper amidodicyanate separate out. Sometimes 
there is also a slight precipitate of copper salts of cyanamide 
and dicyandiamide, which are easily washed out by rapid de- 
cantation, since the copper amidodicyanate is much heavier. The 
copper amidodicyanate has the formula Cu(Q,H 2 N 3 0) 2 4H0O. 
It is further identified by mixing the copper salt with ammonia 
and treating the solution with hydrogen sulphide. The copper 
sulphide is filtered off, and the filtrate concentrated, when a 
white precipitate of thiobiuret is formed. This loses water at 
ioo° and melts at 185 . With copper sulphate a solution of 
thiobiuret gives a white precipitate. 

IDENTIFICATION OF AMMELINE. 

Ulpiani 2 claims that ammeline can be detected in old lime- 
nitrogen as follows : 

Extract the sample with dilute nitric acid. Filter and just 
neutralize the filtrate with ammonia. A white precipitate of 
ammeline is obtained, insoluble in water, soluble in alkalies or 
mineral acids. Analysis should show the solid to have the 
formula C 3 H, 5 N 5 0. 

1 Gaz Chim. Ital 1908, II No. 4, 358-417. 

2 loc. cit. 



CHAPTER IV. 



Storage of Cyanamid. 



On exposure to the atmosphere, Cyanamid absorbs moisture 
and carbon dioxide. This absorption of foreign material, of 
course, increases the weight of the exposed sample, and hence 
decreases the percentage of the original constituents. Neglect 
to observe this increase in weight and corresponding decrease 
of percentages led some early investigators to declare that nitro- 
gen is lost when Cyanamid is stored for any great length of 
time. It has lately been shown by carefully conducted experi- 
ments in the laboratory as well as on a large scale, that under 
conditions of storage customary for fertilizer materials there is 
no loss of nitrogen. 

Factory Test. — When Cyanamid is stored in ordinary burlap 
bags only the exposed surfaces can receive moisture and carbon 
dioxide, and penetration into the interior of the bag or pile is 
necessarily difficult. Even in damp climates, such absorption 
is not very large when considered in its relation to the entire 
pile. Thus, a pile of Cyanamid weighing 94.083 pounds, and 
analysing 15.63 per cent, nitrogen was stored in a warehouse 
over and a few feet above the surface of the St. Johns river at 
Jacksonville, Florida, from July 7th to January 13th, and was 
then carefully weighed and sampled by the purchaser, the 
sample being taken from different portions of two out ot every 
three bags in the lot. 

Per cent, increase 
Weight in weight. 7 mo's 

Original 94.083 .... 

After 7 months- 101,506 7.9 

Hence, even in this damp climate, where rains occur almost 
daily during the summer months, the rate of increase of weight 
is a little more than one per cent, a month, while the nitrogen 
content remains constant. 



Analysis 
nitrogen 

I5-63 


Pounds 
nitrogen 

14,705 


14-52 


14,740 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 25 

Test of Two Bags. — A test on a smaller scale was made by 
the author, at Niagara Falls, Ontario, in 191 2. Two ordinary 
burlap bags, each holding about 150 pounds of Cyanamid 
hydrated on November 12, 191 1, were exposed November 17, 
191 1, on a raised platform made of 4-inch strips spaced 4 inches 
apart. The room was dry, well-ventilated by an open window, 
and kept most of the time between io° and 35 C. Samples 
were drawn and the weight of the bags was taken just before 
they were laid out on the platform. At the end of each period 
of exposure as noted below, the bags were carefully weighed, 
and the contents were removed. After thorough mixing of 
the material a sample was drawn, and the bags were refilled, 
tied, weighed, and again laid out on the platform for further 
exposure. The following data were obtained: 



Bag A. — Analvses. 



Moisture 
Per 
Sample drawn cent. 

Nov. 17, 191 1 0.00 

Dec. 17, 1911 0.40 

Jan. 17, 1912 0.47 

Feb. 17, 1912 0.46 

May 17, 191 2 0.67 



Carbon 

dioxide 

Per 

cent. 


Nitrogen 
Per 
cent. 


Calcium 
Per 
cent. 


N 
Ratio — — 
Ca 


1-75 


16.54 


40.34 


O.4100 


2.12 


16. II 


39-94 


O.4095 


2-75 


16. II 


39-34 


O.4095 


2.87 


I5-96 


33-94 


O.4099 


4-05 


I5-69 


37-94 


O.4136 



Weights. 

Per cent. 

gain in 

weight 

Weight Gain in since 

pounds weight previous 

Date net pounds weighing 

Nov. 17, 1911 148.25 — — 

Dec. 17, 1911 x i50-75 2.50 1.69 

" " " 2 i49- 2 5 

Jan. 17, 1912 150.50 1.25 0.84 

" " " i49-5o 

Feb. 17,1912 150.50 1. 00 0.67 

" " " 150.00 

May 17, 1912 i53- 2 5 3-25 2.17 

1 Before sampling. 

2 After sampling. 



Per cent. 




Per cent. 


nitrogen 
calcu- 
lated 


Per cent. 

nitrogen 

found 


nitrogen 
gained 
or lost 


— 


16.54 


— 


16.266 


16.31 


+ 0.04 


16. 131 


l6.II 


— 0.02 


17.024 


I5-96 


— O.06 


I5-683 


I5-69 


+ O.OI 



26 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 



Bag B. — Analysis. 



Moisture 
Per 
Sample drawn cent. 

Nov. 17, 19 1 1 O.OO 

Dec. 17, 191 1 0.43 

Jan. 17, 1912 0.44 

Feb. 17, 1912 0.46 

May 17, 1912 0.69 



Carbon 

dioxide 

Per 

cent. 

i-75 
2.10 
2.70 
2.83 
3-9 6 



Nitrogen 
Per 
cent. 

16.34 

16.09 

15.87 

I5-70 

I5-50 



Calcium 
Per 
cent. 

40.53 

39-94 

39-35 

38-94 

38.76 



. N 
Ratio—- 
Ca 

0.4031 

0.4029 

0.4033 
0.4031 
0.3999 



Weights. 



Weight Gain in 

pounds weight 

net pounds 

Nov. 17,1911 149.00 

Dec. 17, 1911 '151-75 2.75 

" " " 2 i5o.75 

Jan. 17, 1912 152.25 1.50 

" " " 151-25 

Feb. 17,1912 I5I-75 0.50 

" " " 151-25 

May 17, 1912 154-75 3-5° 



Per cent. 

gain in 

weight 

since 

previous 

weighing 



I.84 
O.99 

0-33 
2.31 



Per cent, 
nitrogen 
calcu- 
lated 



16.046 
15.890 
15.838 
15.480 



Per cent. 

nitrogen 

found 

16.34 

16.09 

15.87 
I5-70 
I5-50 



Per cent. 

nitrogen 
gained 
or lost 



+O.04 
— 0.02 
— O.14 
+0.02 



The addition of free moisture, chemically combined moisture, 
and carbon dioxide necessarily increases the weight of the 
sample, and hence causes a proportionate decrease in the 
percentages of other constituents. It is evident that calcium 
cannot escape from the stored material either by volatilization, 
since calcium compounds require at least a red heat before 
they vaporize appreciably, or by leaching, since the mass re- 
mains practically dry for years. The decrease in calcium per- 
centage must therefore be due solely to the addition of other 
matter, and the ratio of the calcium percentages before and 
after exposure is equal to the inverse ratio of the weights be- 
fore and after exposure. Thus in bag A the ratios are 

40. ■xa 106.^2 •> , 1 • r , 

- — — = = — or there has been an increase of 6.32 per cent. 

37.94 100.00 

on the original weight. As shown by the weighings, the in- 

1 Before sampling. 

2 After sampling. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2"J 

crease of weight was 5.46 per cent, of the original weight. The 
failure of the two results to check more closely is due to the 
difficulty of making accurate calcium determinations in 
Cyanamid. 

Since the absolute quantity of calcium remains constant in 
the mass exposed, it follows that if the absolute quantity of 
nitrogen present do not vary, the ratio of nitrogen to calcium 
must remain constant. Inspection of the data obtained as 
described above shows that this is actually the case within 
sampling and analytical limits of error. Recapitulating the 
results by analysis and by the weights we have : 





Increase in 


weight 




Variation 


of 


nitrogen 




By Ca ratios 


b 


y weighing 


By N/Ca ratio 




By weighing 


Bag A. 


••• 6.32 




5-46 




+O.14 




-fo.oi 


Bag B. 


... 4.77 
■ •• 5-54 




5-57 
5-5i 




— O. IO 




-fO.02 


Average 


+0.02 


+ O.OI5 



There has therefore been no loss of nitrogen under ordinary 
factory conditions of storage, even in the case of a single 
exposed bag, which exposes a relatively larger surface per 
pound of material than a large pile would expose. 

Of the 5.5 per cent, increase in weight, approximately 0.7 
per cent, is due to the addition of free moisture, 2.5 per cent, 
to addition of carbon dioxide, and 2.3 per cent, to addition of 
combined water; or, of the total increase in weight, about 13 
per cent, is due to free moisture, 45 per cent, to carbon dioxide, 
and 42 per cent, to chemically combined water. 

In the analyses given above, free moisture was determined 
by the decrease in weight of a sample heated 5 hours at ioo° 
C, in a drying oven free of carbon dioxide. The "combined" 
water is, properly speaking, not present as water at all, but 
represents water which has acted hydrolytically upon calcium 
cyanamide with the production of various organic derivatives. 
Such hydrolyses are in the main irreversible by drying. The 
increase in weight suffered by a sample of Cyanamid during 
storage cannot, therefore, be determined by simply correcting 
final analyses to the so-called "dry basis," since such a correc- 



28 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

tion is only a small portion of the true correction required. The 
true increase in weight is best determined by direct weighing 
of the initial and final sample, or by comparing the calcium 
content of the initial and final samples. The latter involves 
very accurate calcium determinations, if the results are to be 
significant. 

The absorption of "combined water" and of carbon dioxide 
takes place for the most part in accordance with the follow- 
ing equations, which probably account for the formation of 
dicyandiamide, urea, calcium cyanamide carbonate, and cal- 
cium carbonate: 

2 CaCN 2 + 2H 2 = Ca(CN.NH) 2 + Ca(OH) 2 , 
Ca(CN.NH), + 2H 2 = (H 2 CN 2 ) 2 + Ca(OH) 2 , 
CaCN, + 3 H 2 = CO(NH 2 ) 2 + Ca(OH) 2 , 
CaCN, + C0 2 + H 2 = CaCN 2 .C0 2 .H 2 0, 
Ca(OH) 2 + C0 2 = CaC0 2 + H,0. 

After long periods of exposure there are formed slight 
amounts of secondary derivatives, so that old Cyanamid will 
contain the following substances : 

Calcium cyanamide CaCN 2 

Acid calcium cyanamid Ca(HCN 2 ) 2 

Basic calcium cyanamid CaCN 2 .Ca(OH) 2 

Calcium cyanamide carbonate CaCN 2 C0 2 .H 2 

Dicyandiamide ( H 2 CN 2 ) 2 

Urea CO(NH 2 ) 2 

Amidodicyanic acid H 3 C 2 N 3 (slight amounts) 

Melamine (H 2 CN 2 ) 3 (slight amounts) 

Ammeline H 5 C 3 N 5 (slight amounts) 

Ammonium hydroxide NH 4 OH (traces) 

The following scheme shows the relation of some of these 
forms to each other, and a possible mechanism for their deriva- 
tion from calcium cyanamide : 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2$ 



*/ 



/ 



NCa 



+ 2FL0 



~N 



Calcium 
cyanamide. 



NH, 



Cyanamide. 



+ 2 H 2 



0C< 



.NH„ 



C=NH 
>H + H >° 



Dicyandiamide. 



C-NH 

C=NH 



Melamine. 



V 



/ 



NH 2 



N 



Cyan- 
amide. 



2H,0 



+ H a — 



/NH 2 

/ 
\ 

Urea. 



/NH, 

Nnh 

Amidodicyanic 
acid. 

/NH 2 

C=NH 

Nnh 
c=o 
Nnh 

CC 

~^N 

Ammeline. 



Ca(OH) r 



NH. 



/ 
CO, 

\ 

NH t 

Ammonium 
carbonate. 



+ NH 3 . 



+ NH 3 . 



Relative Amounts of Decomposition Products. — The relative 

amounts of these decomposition products has been studied in 

only a few cases, since the total amounts become appreciable 

only under extraordinarily severe conditions of moisture. A 

test of this kind is reported by Brioux. 1 

1 Annales de la Science agronomique francaise et etrangere, April, 
1910. 



30 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

A sample of lime-nitrogen was exposed on a watch-glass 
in a bell-jar, the atmosphere of which was kept saturated with 
moisture by a beaker of water alongside the watch-glass. The 
10 gram sample after 8 months exposure weighed 18.75 grams. 
The analyses before and after exposure are as follows, the 
third column showing the results corrected to allow for in- 
crease in weight. 

After 
Before After exposure 
exposure exposure corrected 

Total nitrogen 17.08 8.99 16. S4 

Insoluble nitrogen 1.30 0.38 0.71 

Soluble nitrogen in form of Cyanamid I5-Q5 0.14 0.26 

Soluble nitrogen in form of Dicyandiamid 0.25 6.87 12.87 

Soluble nitrogen in "other forms " 0.48 1.60 3.00 

The loss of nitrogen, in the form of free ammonia, has 
apparently been 0.24 per cent. The soluble nitrogen in "other 
forms" consists principally of urea, with a small amount of 
amidodicyanic acid and ammeline. 

The above test is unusually severe, and has little bearing 
upon the question of the storing qualities of Cyanamid. Under 
similar circumstances it takes less than a week for sodium 
nitrate, ammonium sulphate and calcium nitrate to entirely 
dissolve in the moisture they absorb, while basic calcium 
nitrate becomes pasty and sticky in the same time. The 
Cyanamid, on the other hand, is still in good mechanical con- 
dition at the end of eight months. 

A similar test but less severe, and therefore more nearly 
approaching conditions that may occur in storage on a factory 
scale, is the following experiment by G. Henschel. 1 

10 to 11 grams of commercial Cyanamid was placed in a 
thin layer on a watch-glass of about 8 cm. diameter, and set 
in a desiccator jar, in which was a beaker with concentrated 
sulphuric acid and another with distilled water. This provided 
a constant circulation of moist air. In addition, for an hour 
1 Das Verhalten des teehnisclien Calciumcyanamides bei der 
Aufbewalirung sowie unter dem Einfluss von Kulturboden und 
Kolloiden. Inaugural-Dissertation-Univ. of Leipzig, 1912. 



Per cent. 






Dicyan- 




increase 


Total 


Cyanamid 


diatnide 


Urea 


in weight 


nitrogen 


nitrogen 


nitrogen 


nitrogen 


— 


13.09 


12.031 


O.064 


O.694 


6.92 


12.32 


9563 


1. 221 


I.460 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 3 1 

each day during the entire 21 weeks of exposure, a current 
of air was drawn through the desiccator. 

Weight of 
sample 

Original 10.609 g 

After 21 weeks- 11.343 g 

Same corrected 

to original 

weight — — 13-17 10.224 1.305 1.560 

There is therefore no loss of nitrogen, but on the other 
hand an apparent slight gain, probably due, in the belief of the 
experimenter, to loss of moisture before the weighing of the 
sample for analysis. The total increase in weight is 6.92 per 
cent., which is about the same as the increase in the factory 
test at Jacksonville, Florida, described on p. 24. The 
amount of derivatives formed in the latter case was probably, 
therefore, about the same as in the laboratory test by 
Henschel. The amount of dicyandiamide formed is about 
10 per cent, of the total nitrogen, and the urea is about the 
same. 

The agricultural significance of these changes will be dis- 
cussed in a later chapter of this volume. 

The above are a few of the many records at the command 
of the author, all of which agree in showing that when the 
increase in weight is allowed for there is no loss of nitrogen 
in Cyanamid under the ordinary conditions of storage of fer- 
tilizer materials. 



CHAPTER V. 



Decomposition of Cyanamid in the Soil. 

FACTORS INVOLVED. 

When Cyanamid is applied to the soil as a fertilizer it must 
undergo decomposition before the nitrogen can be assimilated 
by plants. The course of this decomposition, however, has 
been in dispute since the adoption of Cyanamid in agriculture, 
and a great deal has been written on the subject. Owing to 
the incompleteness of many of the reports, and the omission 
of essential data, no attempt will be made here to review all 
of them. Of the recent work on the subject the most con- 
sistent seems to be that of .C. Ulpiani and H. Kappen. 

Experiments of Ulpiani. — In 1908 Ulpiani reported the 
results of some experiments 1 that indicate the difficulties sur- 
rounding the solution of this important question. The results 
of these tests are summarized in the table on page 33. 

Aqueous solutions were used containing 0.5 per cent, pure 
cyanamide, together with various added materials as noted. 
Calcium was added in the form of calcium hydroxide, two 
equivalents to one of cyanamide. By "secondary products" 
is meant dicyandiamide, urea, and traces of amidodicyanic 
acid and ammonia, amounting to 33 per cent, of the total 
nitrogen present. Soil was added where shown in the table, 
in the proportion of 10 grams to 100 cc. of solution. The 
"nutritive substance for bacteria" consisted of 0.05 per cent, 
potassium phosphate, 0.01 per cent, asparagine and 0.01 per 
cent, glucose. Bacteria were introduced into flasks 3 to 8 by 
extracting soil with the water to be used to make the cyana- 
mide solution. No bacteria were present in flasks 1 and 2. 
0.4 per cent, chloroform was present in flasks 7 and 8. Deter- 
minations for cyanamide nitrogen in the solutions were made 
at frequent intervals. The percentages of cyanamide decom- 
posed in 4 and 8 weeks respectively are shown in the table : 
1 Gaz. Chim. Ital., 1908, II, No. 4, 358-417. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 33 



Flask 


Calcium 


Secondary 
products 


Soil 


Nutritive 

for 
substance 
bacteria 


Per cent, of cyanamide 
decomposed 

Chloroform 4 wks. 8 wks. 


I. 


Absent 


Present 


Absent 


Absent 


Absent 


0.63 


0.81 


2. 


Present 


" 


i< 


" 


" 


53-25 


73.02 


3- 


Absent 


" 


Present 


Present 


" 


50.50 


83-03 


4- 


Present 


" 


" 


" 


" 


83.00 


100.00 


5- 


Absent 


Absent 


" 


" 


" 


6.84 


16.72 


6. 


Present 


" 


" 


" 


•' 


40.62 


— 


7- 


Absent 


" 


" 


" 


Present 


7.58 


15-52 


8. 


Present 


" 


Absent 


" 


" 


41.04 


— 



Flasks 1 and 2 were not inoculated with bacteria. Flask 1 
therefore shows that a solution of cyanamide, in the presence 
of its derivatives, is not decomposed even upon months of 
standing. The mere addition of lime in sterile conditions 
causes a rapid decomposition of cyanamide. The effect of 
lime is shown throughout by comparing the even-numbered 
flasks with the odd-numbered flasks. 

Flask 7 shows that under sterile conditions, in the absence 
of lime, a small amount of soil causes a small amount of 
decomposition. Flask 5, which differs from flask 7 only in 
the fact that the sterilizing agent, chloroform, was omitted, 
shows that the presence of bacteria had no effect whatever 
upon the decomposition. The same thing is shown by com- 
paring flasks 6 and 8, in which lime was present. 

The larger values obtained in flasks 2, 3 and 4 seem to be 
related in some way to the presence of secondary products, 
that is, dicyandiamide, urea, and possibly amidodicyanic acid 
and ammonia. Flasks 1 and 2 were both uninoculated, hence 
the larger decomposition of flask 2 as compared with flasks 
6 and 8 must be due to the simultaneous action of calcium 
and secondary products of cyanamide. A separate experi- 
ment showed, in fact, that the presence of 0.085 P er cent, 
ammonia in a solution of pure cyanamide containing 0.43 
per cent, cyanamide effected the complete removal of the 
cyanamide in 3 months at 30 C, while the cyanamide without 
an ammonia addition remained constant. 

It is interesting to compare flask 1 with flask 3. These 
differ in two respects, presence of soil and presence of nutri- 



34 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

tive substance. Now soil in the presence of secondary products 
may be expected to act similarly to soil in the absence of 
secondary products, that is, the soil should determine in flask 
3 about 7 per cent, of decomposition more than occurred in 
flask i. The presence of nutritive substance is therefore 
probably in this case the controlling factor, but not nutritive 
substance alone, but nutritive substance in combination with 
soil and cyanamide derivatives. It is quite possible that a 
bacterial decomposition that does not take place in the pres- 
ence of cyanamide alone may take place if other nitrogenous 
substances are present which are capable of being attacked 
by bacteria. In fact, Ulpiani determined by separate experi- 
ments that the soil bacteria employed by him were not able 
to decompose pure cyanamide, but that they grew very readily 
in impure dicyandiamide solutions, while the experiments of 
Kappen show that micro-organisms do take part in the decom- 
position in the presence of nutrient solutions and, with the 
exception of special fungi, in non-sterilized soil. The effect 
of micro-organisms and of glucose used as a nutritive sub- 
stance is shown by the following experiment of Kappen. 1 

One hundred grams of a sand soil of low activity was treated 
with 50 cc. cyanamide solution containing 33 mg. of cyanamide 
nitrogen. The same treatment was given another 100 grams, 
but glucose was added. In another case no glucose was added, 
but the soil was inoculated with cyanamide-splitting clado- 
sporium, a special fungus, occurring in some soils. The sub- 
sequent content of cyanamide nitrogen is shown in the fol- 
lowing table: 

Without 
Cyanamide glucose 

nitrogen in With Without with 

milligrams glucose glucose cladosporium 

Applied 33-°° 33-°° 33-°o 

Analysed immediately 3 x -75 3 2 -°4 3 2 -48 

After 1 day 25.87 23.70 — 

After 2 days 23.52 21.16 4.70 

After 3 days 19-69 *7-93 0.00 

After 7 days 8.33 12.55 

After 9 days 0.00 10.29 

1 Zentr. fur Kunstdiinger Ind. XVII, 251, 1912. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 35 

It will be noticed that on the third day the amount of 
cyanamide that had been decomposed was about the same 
whether glucose were present or not, in fact there seems to 
be slightly more decomposition when the glucose was omitted, 
though this is probably accidental. At the end of 9 days, 
however, the glucose treated sample was entirely decomposed, 
while the untreated sample still contained about one-third of 
the original cyanamide. Cladosporium in the presence of soil 
caused a rapid decomposition, complete in 3 days. It is at 
once evident that the sand soil used did not contain appre- 
ciable amounts of cladosporium, or the decomposition would 
have been more rapid in the first two cases. During the first 
three days the samples with and without glucose behaved very 
much alike, hence the same processes were taking place, and 
these were probably chemical ; then, however, the glucose 
treated sample became suddenly very active, and this prob- 
ably represents the beginning of bacterial participation. 

It should be noted in the above experiment that the concen- 
tration of cyanamide applied was 0.022 per cent., as compared 
with the 0.5 per cent, used by Ulpiani. It is likely that the 
latter concentration is too great to permit bacterial activity, 
except under the most favorable circumstances and then only 
with certain bacteria. The quantity of cyanamide applied by 
Kappen is equivalent to about 600 pounds of nitrogen per 
acre half-foot of soil. In agriculture, 60 pounds per acre is 
a maximum that is seldom exceeded. 

Kappen succeeded in isolating pure cultures of five fungi 
capable of decomposing cyanamide ; two of them, penicillum 
brevicaule, and the cladosporium mentioned above, grew even 
in 2 per cent, solutions, but the others required lower concen- 
trations. It is therefore difficult to estimate the importance 
of these special fungi to this problem. It is certain that they 
do not occur commonly in all soils (those used by Ulpiani 
for instance and the ordinary soils of Kappen) to any great 
extent, and it is doubtful if they ordinarily have much to do 
with Cyanamid decomposition in the soil. 



36 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

Ulpiani explains their action as follows : The fungi may- 
decompose the glucose, when it is present, with the produc- 
tion of various aldehydic substances, which, according to well- 
known chemical reactions unite with the cyanamide with for- 
mation of compounds of the type R.CH : N.CN. It is also 
possible that the fungi produce various products of metabolism 
which are able to react with cyanamide and so neutralize it, 
probably in the manner of the formation of antitoxins. He 
cites in support of this theory the well-known ability of 
penicillum brevicaule to grow in the presence of arsenical 
substances. 1 

The above experiments are in agreement with many others 
by Kappen, as well as with the experiments of Ashby, 2 
Behrens, 3 Stutzer and Reis 4 and others, which show that bac- 
teria are active in some stage of the process. 

From these experiments of Ulpiani, Kappen and others, the 
following facts are evident: 1. A solution of pure cyanamide 
in the absence of other substances is quite stable, and is not 
decomposed by ordinary soil bacteria. 2. A solution of pure 
cyanamide may be decomposed by certain special fungi. 
3. A solution of cyanamide in sterile conditions is decomposed 
by lime, by ammonia, and by soil. 4. A solution of cyanamide 
is decomposed by soil more rapidly in non-sterile conditions 
than in sterile conditions, provided the concentration is not 
too great. 

The course of the decomposition of cyanamide solutions 
by lime is very complex (see also p. 28) and leads to the 
formation of a mixture of urea, dicyandiamide, amidodicyanic 
acid, ammeline, melammine and other complex derivatives. On 
the other hand, the decomposition of cyanamide by soil is a 
simple hydrolysis in accordance with the equation : 

1 B. Gosio, Studio sulla Bioreazione dell 'arsenico tellurio e selenio. 

Roma, Tip, Mantellate, 1907. 

2 Zent. Bakt. XX, 704, (1908) ; XX, 281, (1908). 
s Jahrs. f. Agrik. 121, (1905). 

4 Jour. f. Landw. Vol. 58, 65, (1910). 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2>7 

/NH 2 
CN. NH 2 + H 2 O = OC< 

X NH 2 

The formation of urea is practically quantitative, and is 
determined ordinarily solely by physico-chemical means, with- 
out the participation of organisms. It will be shown later that 
the transformation of the urea to ammonia is probably effected 
by bacteria. 

FIRST STAGE OF DECOMPOSITION. 

The form in which the nitrogen exists in Commercial 
Cyanamid, neglecting for the moment the alterations produced 
in storage, is calcium cyanamide. It has been known for 
many years that this salt is not stable in aqueous solution but 
immediately hydrolyzes to acid calcium cyanamide and calcium 
hydroxide : 

2CN. NCa + H 3 = (CN. NH),Ca + Ca (OH), 

Moreover, all investigators agree that the acid calcium 
cyanamide has but an ephemeral existence in the soil ; when 
applied in normal fertilizer doses the calcium quickly abandons 
the cyanamide. Lohnis attributes this action to the effect of 
carbon dioxide in the soil solution, precipitating the calcium 
as carbonate and setting free the cyanamide : 

(CN.NH) 2 Ca + C0 2 = zCN.NH, + CaCO, 

Kappen considers the removal of calcium as a physical 
process of absorption in the soil, with simultaneous hydrolysis 
to free cyanamide : 

(CN.NH) 2 Ca + 2H 2 = 2CN. NH, + Ca(OH) 2 . 

He found, for instance, that when 200 grams of clay soil was 
shaken with 250 cc. of a solution of lime-nitrogen containing 
47.8 mg. calcium and 62.2 mg. nitrogen, 39 per cent, of the 
calcium and only 5 per cent, of the nitrogen was absorbed by 



38 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

the soil in one hour. Such a fertilization, however, amounts 
to 560 pounds nitrogen per acre half-foot of soil, a quantity 
far in excess of any ever used in agriculture. The quantity 
of calcium absorbed in one hour in this test is equivalent to 
600 pounds CaO per acre half-foot of soil. 

Ulpiani regards the change as taking place with the inter- 
mediate formation of calcium cyanamide carbonate : 

(CN. NH) 2 Ca + C0 2 = CN. NH 2 + CaCN 2 C0 2 , 
CaCN 2 C0 2 + H 2 = CN. NH 2 + CaCO :) 

Whatever the mechanism of this hydrolysis there is no 
question but that the result is free cyanamide, and conse- 
quently the following investigations on the decomposition of 
cyanamide in the soil were made with the free cyanamide, 
CN.NH,. 



SECOND AND THIRD STAGES OF DECOMPOSITION. 

The following experiment by Ulpiani 1 was made to deter- 
mine the rate of decomposition of cyanamide: 100 grams of 
earth carefully dried at laboratory temperature, and sieved 
through a screen with holes of 1 mm. diameter, was placed in 
a glass tube and to it was added 20 cc. of a solution of pure 
cyanamide containing 4.2 per cent, cyanamide. The liquid 
reached almost to the bottom of the tube, hence the soil was 
not quite saturated. A series of tubes so prepared was stop- 
pered with cork and set in a thermostat at 28 C. After 
various periods of time the content of cyanamide remaining in 
the tubes was determined as follows : 80 cc. of distilled water 
was added and thoroughly stirred with the contents of the 
tube. After exactly an hour the contents were filtered with 
suction. Of the filtrate (about 70 cc), two portions of 25 cc. 
each were analyzed for cyanamide. The following results 
were obtained : 

1 Gaz. Chim. Ital. XL, Parte 1, 1910. 



CYANAMID MANUFACTURE, CHEMISTRY AND USES 



39 



Quantity of eyanamide 
Milligrams 

Initial 84.0 

After % hour 79.2 

After 6 hours 75.8 

After 1 day 65.9 

After 3 days 52.5 

After 5 days 40.9 

After 7 days 29.8 

After 9 days 22.6 

After 11 days 18.4 

After 15 days 10. o 

After 18 days 00.0 

The values obtained are plotted in Fig. 2. It is seen that 
the removal of eyanamide from the soil solution is a maximum 




"? — 5 7 1 ?. 

Days after appl/cat/on 

RATE OF REMOVAL OF CYANAMIDE 
FROM SOIL SOLUTION. 

Fig. 2. 

in the first few moments of contact. This probably corre- 
sponds to an initial period of absorption. It is evident, how- 
4 



4-0 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

ever, that the cyanamide is not removed solely by a process 
of absorption, since it is characteristic of absorption processes 
that a state of equilibrium is usually reached between the sub- 
stance in solution and in the absorbing surfaces within a day. 
The substance that is being absorbed never disappears entirely 
from the solution. In the present experiment, the reaction 
proceeds to complete disappearance of the cyanamide. The 
rate of removal of cyanamide is practically constant after the 
first 9 days, and shows no tendency to become zero thereafter, 
as it would if an equilibrium were being approached. Such 
rapid removal of the cyanamide to the very end of the experi- 
ment can be due only to chemical conversion of the cyanamide 
to other forms. 



INFLUENCE OF CONCENTRATION. 

The following experiment was made by Ulpiani to deter- 
mine the effect of varying the concentration of cyanamide. 
In each of a series of glass tubes was placed ioo grams of 
soil, which was covered with 25 cc. of a solution of cyanamide 
at various concentrations. At the end of 3 days and at the 
end of 10 and 30 days, certain tubes, as shown in the table, 
were taken out, thoroughly mixed with 75 cc. water and after 
standing one hour were filtered with suction, and cyanamide 
was determined. The following results were obtained : 



Initial quantity 
of cyanamide 


-, Final quantity of cyanamide 

After After After 
3 days 10 days 30 days 


Absolute 

quantity 

converted 

in 3 days 

Mg. 




Concen- 
tration 
Per cent. 


Mg. 
in 25 cc. 


Percentage 
converted 
in 3 days 


I 


25.O 


trace 


— 


— 


25.O 


IOO 


2 


50.O 


25-1 


— 


— 


24.2 


49 


3 


75-o 


43-5 


— 


— 


31-4 


42 


4 


100.0 


60.0 


— 


— 


40.0 


40 


5 


125.0 


84.0 


— 


— 


41.0 


33 


6 


150.0 


103.4 


— 


— 


46.5 


31 


9 


225.0 


I7I-3 


110.8 


13-4 


53-7 


24 


12 


300.0 


231.8 


156.8 


40.3 


68.2 


23 


15 


375-o 


302.4 


209.1 


60.5 


72.6 


19 


18 


450.0 


352.8 


245-2 


67.2 


97.2 


21 


21 


525-° 


420.0 


289.8 


71.4 


105.0 


20 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 41 

In Fig. 3 is plotted the percentage of the cyanamide removed 
with increase of concentration. This percentage is a maximum 
at the lower concentrations, but decreases as the concentration 
increases, until finally a steady value of about 20 per cent, is 
reached, when the amount of cyanamide disappearing in a 
given time is constant. The fact that this curve is approxi- 
mately logarithmic indicates that the primary action is one of 
absorption, since it is well-known that the more dilute the solu- 
tion the greater is the percentage of substance taken up by the 
absorbing surfaces, and that as the concentration of solution 



EFFECT OF CONCENTRATION 
ON REMOVAL OF CYANAMIDE 
FROM SOIL SOLUTION. 




j 0.2 0.3 0.4 05 

Fig. 3- 

increases a condition of equilibrium is reached and the ratio 
of the concentrations in the absorbing surfaces and in the 
solution becomes constant. 

Fig. 4 shows the absolute quantity of cyanamide removed as 
the concentration increases. It is practically directly propor- 
tionally to the concentration. This curve shows the same 
fact as the curve in Fig. 4, namely, that the ratio of the con- 
centrations in the absorbing surfaces and in the solution is 



42 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

a constant, a fact highly characteristic of absorption pro- 
cesses. 

In this experiment also, the cyanamide finally disappears 
entirely from the solution in the course of time, and hence, 
chemical conversion occurs along with the absorption 
phenomena. 

Taking all the above facts together, it is easy to under- 
stand that in the initial period of contact between the cyanamide 
solution and the soil there is a withdrawal of cyanamide mole- 
cules from the solution, and a concentration of molecules in 

Grams Cyanam/e/e app/tea 
per lOO grams So//. 




Fig- 4- 

the limiting stratum between the solution and the surface of 
the solid soil particles. Along with and subsequent to this 
absorption process there is a chemical conversion of cyanamide 
molecules, by catalytic action of soil colloids, as we shall show 
later, the products of the reaction being removed continually 
and being replaced by new molecules of cyanamide in the limit- 
ing stratum. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 43 

That bacteria could take no part in the present experiment 
is evident, since micro-organisms cannot live in the very con- 
centrated solutions employed. 

INFLUENCE OF TEMPERATURE. 

Experiments carried out in a similar manner with 100 grams 
of soil and 20 cc. of solution containing 4.2 per cent, cyanamide 
at various temperatures gave the following results : 



At o° 



At 12° 



At 30 



Initial quantity of cyananiide- • • 


. 84 


tug. 


84 nig. 


84 mg 


Quantity present after 2 days. • . 


77 




69 




5i 


" 4 " ••• 


• 73 




59 




23 


" 6 " ... 


. 69 




44 




18 


" 11 " ... 


- 53 




33 




trace 



The velocity of the reaction increases with the temperature, 
but even at o°, where micro-organic life is practically at a 
standstill, there is a conversion of about 3.5 mg. of cyanamide 
per 120 grams of damp soil per day. 



INFLUENCE OF SOIL AT 100° C. 

Two flasks, one containing ioo cc. of a solution with 21 per 
cent, cyanamide, the other 100 cc. of 21 per cent, cyanamide 
solution and 500 grams of soil, were heated in a Koch's oven 
at ioo° C. for six hours. After cooling, 400 cc. of water was 
added to each, and after agitation and filtering, analyses were 
made. In the flask without soil there was still a large quantity 
of cyanamide present and considerable dicyandiamide. In the 
flask with soil, however, there was no cyanamide or dicyandia- 
mide remaining after the treatment, but abundant quantities of 
urea. Under these conditions it is probable that the conver- 
sion to urea is quantitative. The reaction must be one of 
hydrolysis in accordance with the equation. 



,NH„ 



CN. NH 2 + H.,0 — OC 



\ 



NH, 



44 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

NATURE OF PRODUCTS FORMED IN SOIL AT ORDINARY 
TEMPERATURES. 

The formation of dicyandiamide is always accelerated by the 
action of heat, whether in solutions of cyanamide, or in solu- 
tions of cyanamide treated with lime, ammonia or other weak 
bases. Since there is no formation of dicyandiamide when 
cyanamide is heated with soil, as shown in the experiment on 
page 43, there will evidently be none formed at ordinary tem- 
peratures. This is verified in the following two experiments. 

Four kg. of soil in a balloon flask was sterilized on three 
successive days by heating for an hour each day in an auto- 
clave at ioo° ; then was introduced into the flask 800 cc. of a 
solution containing 4.2 per cent, cyanamide. The flask was 
stoppered and kept in a thermostat at 25 for 18 days. After 
agitation with 3,200 cc. water for an hour, and filtering with 
suction, total nitrogen and cyanamide nitrogen were deter- 
mined. The results were as follows : 

Grams 

Initial nitrogen 2.492 

Nitrogen absorbed in soil 1.154 

Nitrogen in solution as cyanamide 0.671 

" " not cyanamide 0.667 

" " as dicyandiamide none 

After the removal of the cyanamide, and concentration on the 
water bath, addition of nitric acid produced an abundant pre- 
cipitate of nitrate of urea, which on recrystallization showed a 
melting point of 140 . This experiment shows that under 
sterile conditions the product of cyanamide conversion is prob- 
ably entirely urea. 

Under natural conditions, there is little doubt but that the 
urea is rapidly converted in the soil into ammonium com- 
pounds. It was desirable therefore to learn how closely the 
action of cyanamide resembled that of ammonium carbonate 
in the soil. In a balloon flask containing 11 kg. of soil was 
added 200 cc. of solution containing 4.2 per cent, pure cyana- 
mide ; and in another flask with 1 1 kg. of soil was added 200 
cc. of solution containing 9.6 per cent, ammonium carbonate, 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 45 

equivalent to the amount of cyanamide used. Each flask was 
equipped with connections permitting a current of air to pass 
through the flask, and then through a bottle of dilute sulphuric 
acid to catch any ammonia evolved in the flask. The balloon 
flasks were held in a thermostat at 25 ° for 22 days, at the end 
of which time 800 cc. water was added. After shaking and 
standing an hour and filtering with suction, tests showed that 
there was no cyanamide or dicyandiamide present in the flask 
to which cyanamide had been added. Determinations were 
made for total nitrogen, ammoniacal nitrogen and nitric nitro- 
gen in the solution. 

The following values were obtained : 

Soil plus 
Soil plus ammonium 

cvanamide carbonate 

nig. mg. 

Iuitial nitrogen 560 560 

Final nitrogen absorbed by soil. 450 420 

Final nitrogen remaining in solution : 

Ammoniacal 60 70 

Nitrate 9 70 

Cyanamide o — 

Dicyandiamide o 

Undetermined 41 o 

The sulphuric acid in the bottles, through which bubbled the 
air leaving the flasks, was unchanged, hence, no ammonia 
escaped from the soil. 

Since the 41 mg. of undetermined nitrogen in the solution 
from the cyanamide flask was not cyanamide, dicyandiamide, 
ammonia or nitrate nitrogen, it must have been urea, in accord- 
ance with the previous experiment. The conversion of the 
urea to ammonium salts was therefore not quite complete. The 
conversion of ammonium salts to nitrates was also less than 
the conversion in the case of ammonium carbonate. The 
amount of ammoniacal nitrogen in solution is practically equal 
in the two flasks. It is evident, therefore, that in both cases 
the absorbed nitrogen exists in the soil in the state of am- 
monium salts, and these are in equilibrium with the ammonium 
salts in the solution. Since the soil was not sterilized and low 



46 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

concentrations of cyanamide were used, and large quantities of 
ammonia were formed, it is very likely that bacteria partici- 
pated in the decomposition by reacting upon the urea and 
determining its hydrolysis to ammonium salts. 

EFFECT OF CHANGING RATIO OF LIQUID TO SOIL. 

When 100 grams of air-dried earth was covered with 20 cc. 
of cyanamide solution practically all of the soil was wetted, 
only a little at the bottom of the tube remaining dry. In this 
condition the mass of water may be considered as being at its 
maximum distension, each solid particle of the soil being sur- 
rounded by a thin film of liquid. This liquid film on the in- 
side, is in contact with a solid phase, and on the outer surface 
with a gaseous phase, since the interstices of the soil were not 
filled with liquid. 

When 100 grams of soil was covered with 50 cc. of 
cyanamide solution the interstitial spaces were filled with 
liquid. There was therefore practically no gaseous phase 
present. 

One hundred grams of soil covered with 100 cc. of 
cyanamide solution was completely submerged. Series III in 
the table was thoroughly shaken twice a day during the test. 
Series IV was not disturbed in any way. The results obtained 
were as follows : 











Series I 


Series II 




Series IV 










20 cc. 

not 

shaken 


50 cc. 

not 

shaken 


Series III 
100 cc. 
shaken 


100 cc. 

not 

shaken 










nig. 


nig. 


mg. 


rag. 


Initial 


quantity Cyanauiid 


• 84.O 


84.O 


84.O 


84.O 


Quantity 


after 


1 day 


• 65.9 


68.O 


71.9 


73-° 


(i 




" 


5 days 


• 40.9 


53-7 


58.1 


60.0 


n 




" 


9 days 


. 22.6 


47-8 


54-6 


57-i 


" 




" 


15 days 


• IO. O 


34-8 


46.2 


49-5 


n 




" 


21 days 


• OO.O 


26.7 


35-7 


44.1 


1 1 




" 


31 days 


. O.O 


11. 7 


35-2 


36.9 


" 




" 


41 days 


• O.O 


8.4 


18.6 


33-6 



Here again we must exclude bacterial participation, since if 
bacteria were present they should grow better in the dilute 
solutions than in the solution of 4.2 per cent, cyanamide in 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 47 

Series I, yet in the dilute solutions the transformation is very 
slow. 

The above experiment shows that the cyanamicle does not 
react with other soluble substances of the soil, for in such case 
the maximum activity should occur in dilute solutions ; but its 
conversion is at a maximum when the greatest amount of 
cyanamide is enabled to come in contact with the solid sur- 
faces of the soil particles. This condition is obtained when 
for a given quantity of cyanamide the amount of liquid is a 
minimum, for then the liquid film about the solid soil particles 
is its thinnest, the cyanamide is closest to the soil, and the 
forces of surface tension are at their maximum. 

INFLUENCE OF AERATION. 

In order to determine whether oxidation plays any part in 
the phenomena, an apparatus was arranged so that a current 
of air in one case and a current of hydrogen in another could 
be conducted over the samples of soil treated as before with 
4.2 per cent, cyanamide solution. The treatment lasted for six 
days, a portion of the sample being withdrawn in three days. 
The following: results were obtained : 



Quantity cyanamide present 

Initial r- — ' > Per cent. 

quantity after after Cyanamide converted in 

cyanamide 3 days 6 days , " > 

Mg. Mg. Mg. 3 days 6 days 

Air 168.0 no.o 22.0 34.0 86.0 

Hydrogen.. 168.0 114.0 46.0 32.0 72.0 

There is practically no difference in the amounts of conver- 
sion in 3 days, and not a great deal of difference between the 
amounts of conversion in 6 days. The results do not differ 
enough so that it can be said that oxidation plays any appreci- 
able part in the change. The fact, therefore, that in all of the 
preceding experiments the tubes were stoppered with cork and 
sealed with paraffin to prevent evaporation of water could not 
at any rate increase the conversion. 



48 CYANAMII>— MANUFACTURE, CHEMISTRY AND USES 

INFLUENCE OF ELECTROLYTES. 

To determine the effect of the presence of various reagents 
on the course of the conversion, an experiment was made with 
solutions of cyanamide in balloon flasks without addition of 
soil, but with various electrolytes. The concentration of 
cyanamide in the solution was 0.554 per cent. ; the other reag- 
ents were in the proportion of two equivalents to one 
cyanamide. The following table shows the amounts of 
cyanamide remaining in solution. 

554 mg. cyanamide plus 
After — Ca(OH) 2 KOH HN0 3 KN0 3 

— weeks 554.0 557.0 556.0 451.0 558.0 

3.3 weeks 554-° 413.0 420.0 254.0 422.0 

8.3 weeks 554.0 369.0 382.0 — 369.0 

13.3 weeks 554.0 331.0 340.0 — 303.0 

28.3 weeks 554-Q 182.0 trace — trace 

The very slow course of the reactions as compared with 
the action of soil shows that it is probably not the soluble 
salts in the soil that are responsible for the hydrolysis of 
cyanamide but the solid soil particles. 

This confirms the conclusion drawn on page 42. 

NATURE OF EFFECTIVE SOIL CONSTITUENTS. 

In order to determine whether the conversion of cyanamide 
is caused by the gross solid particles of mineral matter in the 
soil, or whether it is due to colloids, or various organic debris, 
the following experiment was made. Soil was allowed to 
stand a week in contact with concentrated hydrochloric acid, 
and was then washed free of acid. A portion of soil so 
treated was saturated with sodium carbonate solution and 
then washed free of alkaline reaction. A fresh portion of 
soil was calcined by heating in a combustion furnace in a 
current of oxygen until carbon dioxide no longer escaped. 
These samples were treated with cyanamide solutions as in 
previous experiments, with the following results: 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 49 

Final cyanamide 

Initial after after after 

cyanamide 3 days 6 days 9 days 

mg. mg. mg. mg. 

Ordinary soil 83.8 52.0 36.0 19.5 

Soil treated with HC1 S3.8 63.5 49.1 36.0 

Soil treated with H CI and Na 2 CO s .. 83.8 55.5 43.2 46.0 

Soil calcined 83.8 77.6 

Each of the above treatments has diminished the ability of 
the soil to convert cyanamide to other forms. The calcined 
soil has very little power of decomposition. It is evident, 
therefore, that it is not the gross, solid, mineral particles of 
the soil that have this power, but certain constituents of the 
soil mass that are destroyed by heat. These constituents 
belong to the class of chemical compounds that form colloids 
or disperse systems in the soil. 

We will now examine the results of experiments made with 
various materials that are known to form part of practically 
all soils. 

EFFECT OF ZEOLITES. 

According to Van Bemmelen 1 the colloids of agricultural 
soil consist principally of amorphous zeolites (amorphous 
hydrated silicates). These remain for an indeterminate time 
in suspension in pure water, are coagulated by electrolytes, 
can be dried into hard compact masses, have in the highest 
degree the properties of hydrogels, and to their presence is 
probably due the greater part of the absorptive powers of 
the soil. Since these substances could not be isolated in their 
natural state it was necessary to use certain crystallized 
zeolites, as follows : 

Natrolite of Bohemia, hydrated metasilicate of aluminium 

and sodium. 
Scolecite of Ireland, hydrated metasilicate of aluminium and 

calcium. 

1 Landw. Ver. Staz. Bd. XXXV, (1888) p. 69. 



50 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

Analcimite of Tyrol, hydrated trisilicate of aluminium and 
sodium. 

Cabasite of Nova Scotia, hydrated trisilicate of aluminium 
and calcium. 

Each zeolite was ground in a mortar and made to pass a 
screen of fineness Kahl. oo. 

One hundred grams of each zeolite was placed in glass tubes 
moistened with 20 cc. of a 4.2 per cent, solution of cyanamide 
(2.8 per cent, nitrogen). A fifth tube without zeolite was used 
as a control. After 12 days in a thermostat the solutions were 
analyzed with the following results : 

Cyanamide 
Initial after 

cyanamide 12 days 

grams grams 

Solution alone 0.0840 0.0836 

" natrolite 0.0840 0.0235 

" scolecite 0.0840 0.0148 

" analcimo 0.0840 0.0158 

' ' cabasite 0.0840 0.0168 

This experiment shows that the crystalline zeolites possess 
to a high degree the ability to transform the cyanamide, from 
which we may conclude that the colloidal zeolites as they exist 
in the soil must have a still greater ability. The crystalline 
zeolites, according to Zambonini, 1 have a structure analogous 
to that of the hydrosols, and according to Von Weimarn 2 may 
act like colloidal substances. 

EFFECT OF CARBON. 

Ulpiani next desired to learn what effect would be obtained 
with a material exposing a large surface, but of no chemical 
activity towards cyanamide. For this purpose a commercial 
animal carbon was washed with hydrochloric acid and then 
with water until free from acid, and was dried in an oven at 
no° C. In order to obtain a wetting comparable to that in 
the experiments with soil, 50 grams of carbon was moistened 

1 Atti. R. Ace. Lincei, XVIII. fasc. II, 1st Sem, 1909. 

2 Koll. Zeit. Vol. VI, No. 1, 1910. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 5 I 

with 50 cc. of 4.2 per cent, cyanamide solution. The tubes 
were kept in a thermostat at 25 for different lengths of time. 
Just before the analysis 200 cc. of water was added, stirred 
for exactly one hour, filtered with suction, and cyanamide was 
determined in the filtrate. The results were as follows: 



Cvanamide present Total nitrogen in solution 

mg. Per cent. nig. Per cent. 

Beginning 210.0 100 140 100 

After 1 hour 161. 7 77 112 80 

" 6 hours 153.3 73 io 5 75 

" 1 day 132.3 63 102 73 

" 3 days 107.6 51 87 62 

" 5 " 96.6 46 89 64 

" 7 " 75-6 36 89 64 

" 9 " 59-3 2S S3 59 

" 15 " 8.4 4 64 46 

" 22 " 0.0 o 77 55 

On the 22nd day the solution was distilled with magnesia, 
giving up 66 per cent, of its nitrogen as ammonia. Hence, of 
the 55 per cent, remaining in the solution on the 22nd day 22 
per cent, was ammoniacal and 33 per cent, ureic nitrogen. A 
test with nitric acid gave characteristic crystals of urea nitrate. 
The experiment was repeated, sterilizing both the carbon 
and the cyanamide solution. After 2 months the following 
results were obtained : 

Mg. 

Initial nitrogen 560 

After 2 months, ammoniacal nitrogen 8 

Cyanamide " o 

Dicyandiamide " o 

A test for urea showed the presence of abundant quantities. 

These experiments with carbon show that the decomposition 
of cyanamide is an hydrolysis which is greatly accelerated by 
the addition of catalysers of various kinds. 

EXPERIMENTS WITH NATURAL COLLOIDS. 

The experiments of H. Kappen 1 confirm in general the 
results obtained by Ulpiani. The following experiment of 
1 Zentr. f. Kunstdtinger-Industrie, XVII, 234-236, 248-251, 1912. 



52 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

Kappen shows the relative decomposing ability of some well- 
known constituents of ordinary soils. These materials were 
selected so as to differ as widely as possible from one an- 
other, so that the effect of individual constituents might stand 
out. Each substance was used in its natural condition, with- 
out being sterilized, but ground to a fine powder. They are 
all in the class of compounds that form gels in the soil. 

i. Meadow iron ore from Guben, Niederlausitz; contain- 
ing considerable manganese. 

2. Meadow iron ore from Otrotschin, Bohemia; contains 

no manganese. 

3. Earth of Siena, yellow natural product containing iron 

oxide. 

4. Umber, brown natural product containing iron and man- 

ganese oxides. 

5. Laterite earth from Kamerun. 

6. Manganese ore, principally manganese hydroxide. 

7. Manganese dioxide. 

8. Red Bauxite, aluminum hydroxide gel containing iron 

oxide. 

9. White Bauxite, without iron oxide. 

10. Kaolin from Meissen. 

11. Sandy Kaolin from Tiirkismuhl. 

12. Glass sand. 

Of the above minerals No's 1, 2, 3, 4, 6, 7, 8, 9 and 12 
were used alone, while No.'s 5, 10 and n were mixed with an 
equal quantity of glass-sand. One hundred grams of each was 
placed in an Erlenmeyer flask and treated with 10 cc. of a 
0.5 per cent, cyanamide solution, containing 33 mg. cyanamide- 
nitrogen. Immediately after the addition of cyanamide, and 
at the end of various periods of time the content of cyanamide- 
nitrogen was determined, with the following results: 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 53 



Cyanamide 
nitrogen 


1. 
Iron 
ore 


2. 
Iron 
ore 


3- 

Earth 

of Siena 


4- 
Umber 


5- 
L,aterite 


6. 
Manganese 
hydroxide 






33- 00 


33-°° 


33-oo 


33-°o 


33-Oo 






After y z hour- 


•- 22.96 


33- is 


33-51 


31-75 


34.02 


8.00 


" 1 day- - • 


O.OO 


0.00 


32.04 


20.03 


19.40 


0.00 


" 2 days - • 


.. — 


— 


30.87 


13-27 


II. 17 


— 


" 3 days • • 


— 


— 


27.3S 


5-92 


— 


— 


" 6 days • - 


•• 


— 


27.04 


0.00 


4-37 


— 


" 7 days - - 


— 


— 


26.57 


— 


2.82 


— 


Cyanamide 
nitrogen 


7- 

Manganese 

dioxide 


8. 

Red 

bauxite 


9- 
White 
bauxite 


10. 
Kaolin 


11. 

Sandy 
kaolin 


12. 
Glass 
sand 






33-oo 


33-oo 


33-00 


33-00 


33-oo 






After y z hour- 


•• 30-49 


32.48 


33-04 


32.04 


32.00 


32.00 


' ' 1 day - - - 


•• II.76 


29.40 


32.04 


32.04 


26.16 


32-34 


" 2 days - - 


O.OO 


27-34 


30.86 


31.16 


21-75 


32-34 


' ' 3 da g s • • 


— 


25.28 


30.57 


30.57 


— 


32-34 


" 6 days • • 


.. — 


19.82 


30.28 


30.28 


1352 


32.34 


" 7 days - - 


•• — 


17.68 


29.98 


29.98 


11.76 


32.24 



Of the greatest activity is manganese hydroxide; second, 
iron hydroxide containing manganese hydroxide ; and third, 
iron hydroxide free of manganese. The activity of the next 
most active materials can properly be ascribed to their con- 
tents of iron oxide. The difference in the activity of red and 
white bauxite is very likely due to the difference in iron con- 
tent. The greater activity of sandy kaolin as compared with 
kaolin is probably due to the presence in the former of zeolitic 
substances, which, as Ulpiani found, have a high activity. 

The low activity of the kaolin, considering the large specific 
surface it possesses, suggested that the properties of the vari- 
ous substances are not merely surface phenomena, but that 
their specific chemical nature is of importance. Manganese 
hydroxide and the two iron ores were mixed with glass sand 
in the proportion of 1 gram to 100 grams sand, and a sample 
of 0.1 gram manganese hydroxide with 100 grams glass sand. 
These mixtures moistened as before with cyanamide solution 
containing 33 mg. nitrogen, gave the following results, as com- 
pared with the kaolin of the preceding experiment : 



54 



CYANAMID — MANX 


JFACTURE, 


CHEMISTRY 


AND U 


SES 








Glass-sand plus 






Cyanamide 

nitrogen 
milligrams 


Kaolin 


1 per cent, 
manganese 
hydroxide 


1 per cent. 1 
iron ore 
No. 1 


per cent, 
iron ore 
No. 2 


0.1 percent, 
manganese 
hydroxide 




• 33-oo 


33- 00 


33- 00 


33- 00 


33-°° 


^.fter 15 hours. . 


• — 


5.06 


25-25 


30.80 


— 


" 2 days- • • 


• 31-16 


0.00 


14.78 


26.48 


30.18 


" 3 " ••■ 


•• 30.57 


— 


8.62 


22.79 


28.33 


" 6 " ... 


. 30.28 


— 


4.00 


17.24 


25-25 



It has been shown in the preceding experiment that glass 
sand has practically no activity. Hence, 0.1 grams of man- 
ganese hydroxide is more effective than 100 grams of kaolin. 
The surface exposed by the kaolin is clearly much greater than 
that exposed by the smaller quantities of iron and manganese 
hydroxides, and the catalytic activity of the latter is therefore 
essentially connected with their chemical properties. 

Another experiment was made to compare the activity of 
iron hydroxide, aluminium hydroxide and silicic acid. The 
iron and aluminium hydroxides were prepared by precipita- 
tion ; a sample of each was mixed in the undried condition with 
4 times its weight of glass sand, the mixture then containing 
2.6 per cent, iron oxide in the one case and 1.6 per cent, 
alumina in the other. The aluminium hydroxide and the pre- 
cipitated silicic acid were dried and applied separately to twice 
their weight of glass sand. One hundred grams of each of 
the above mixtures was treated with 20 cc. of cyanamide solu- 
tion containing 33 mg. of cyanamide nitrogen. The sub- 
sequent analyses are as follows : 







Glass 


-sand plus 




Cyanamide 
nitrogen in 
milligrams 


Iron 
hydroxide 

undried 
2.6 # Fe 2 3 


Aluminium 

hydroxide 

undried 

1.654 A1 2 3 


Aluminium 

hydroxide 

Dried 


Silicic 
acid 
Dried 




33-°° 


33-oo 


33- 00 


33- 00 


After y z hour • 


3I-52 


32.48 


32.04 


32.92 


" 1 day • • 


O.OO 


32.34 


3I.I6 


32.63 


" 3 days .. 


— 


29.56 


29.69 


31-94 


" 6 days . . 


— 


— 


25-87 


31.08 



Silicic acid has a slight ability to convert cyanamide; and 
aluminium hydroxide has somewhat more. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 55 

To determine the effect of varying quantities of iron 
hydroxide gel, the precipitated undried hydroxide was mixed 
with glass sand in different proportions, and treated as above 
with the following results : 

Cyanamide Glass-sand plus iron hydroxide gel containing 

nitrogen in , ■ ■ 

milligrams 2.6£ Fe 2 3 i.3# Fe ; 3 0.65 £ Fe : 3 0.26$ Fe 2 3 

Applied 33.00 33.00 33.00 33.00 

After 1 day 0.00 4.31 12.32 23.11 

" 2 days — 0.00 3.69 13-55 

" 3 " — — trace 9.85 

" 4 " .... — — 0.00 8.00 

" 5 " •••• 5-37 

The amount of conversion, therefore, varies with the amount 
of iron oxide present. 

The same iron hydroxide gel was treated in different ways 
to see what effect would be obtained by changing the form of 
the material : 

Precipitated iron hydroxide 

Cyanamide Dried Heated in 

nitrogen in 5 hrs. at steam for Ignited 

milligrams Untreated io5°C 2^ hrs. for % hrs. 

Applied 33.00 33.00 33.00 33.00 

After y 2 day — 4.31 12.32 — 

After 1 day 0.00 0.00 6.46 14-47 

" 2 days — — 1.57 6.16 

" 3 " — — 0.00 4.00 

" 4 " — — 1-84 

" 5 " — °-°° 

The untreated iron hydroxide has the most activity, which is 
decreased somewhat by steaming and greatly decreased by 
ignition. 

To determine the effect of iron oxide in the condition of a 
hydrosol, 250 cc. of iron oxide sol containing 0.8 per cent, iron 
oxide was treated with 1.25 grams cyanamide. The solution 
remained clear and fluid during the course of the experiment. 
For the determination of cyanamide, 10 cc. of the clear solu- 
tion was pipetted off, flocculated with ammonium nitrate and 
after dilution and filtration, treated in the usual manner. The 
following results were obtained : 
5 



56 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

Cyanamide 

nitrogen in Iron oxide sol. 

milligrams (0.8 per cent. Fe 2 O3) 

Applied 33.04 

After 18 hours 27.77 

" 2 days 22.40 

" 4 days 10.08 

The condition of sol is favorable to the conversion, but not as 
favorable as the condition of gel since the dilution of the 
cyanamide hinders the reaction. 

In order to determine whether or not calcium cyanamide 
reacts as readily as cyanamide, a quantity of lime-nitrogen con- 
taining 33 mg. of cyanamide nitrogen was added to ioo g of a 
mixture of sand with equal weights of manganese hydroxide, 
and iron ores No. I and 2, (see page 52). After 24 hours 
the quantities of cyanamide nitrogen remaining were : 

Milligram 

Manganese 0.00 

Iron ores No. 1 and No. 2 0.00 

Glass-sand 29. 18 

With cyanamide, glass-sand left 32.34 mg. in solution after 1 
day. The presence of the lime in the lime-nitrogen evidently 
hastens the decomposition of the cyanamide. 

The effect of pure, calcined iron oxide, Fe 2 3 , on 
cyanamide was determined by mixing glass sand with 5 per 
cent, of its weight of iron oxide, and treating with cyanamide 
solution as in the previous experiments. 

Milligram 

Cyanamide applied 33-oo 

" after 1 day 32.42 

" 3 days 30.63 

" 5 days 28.07 

" " 8 days 26.56 

Iron oxide therefore has a slow action as compared with the 
metal hydroxides used. 

EXPERIMENT WITH STERILIZED SOIL. 

All of the above experiments of Kappen were made with 
unsterilized materials; they therefore do not differentiate 
between physico-chemical and bacterial processes. In this 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 57 

experiment, soil was sterilized by being held several days in 
an atmosphere of chloroform vapor, and was compared with 
untreated soil as in the previous experiments, with the follow- 
ing results : 

With chloroform Without chloroform 
mg. nig. 

Cyanamide nitrogen applied 33-°° 33-°° 

Cyanamide nitrogen after 2 days • • • 23.00 0.00 

The addition of chloroform to the soil therefore greatly hin- 
ders the decomposition of the cyanamide, but does not prevent 
it. It is quite probable that in all of the experiments made by 
Kappen, except those where high temperatures were employed, 
bacteria participated in the decomposition of the cyanamide 
by converting the urea into ammonium salts, thus hastening 
the hydrolysis of the cyanamide. 

CONCLUSIONS. 

From the above experiments on the conversion of cyanamide 
the following conclusions can be drawn : 

I. Calcium cyanamide in contact with moist soil undergoes 
a decomposition to the form of ammonium salts in three inde- 
pendent stages. The first stage is a complete hydrolytic sepa- 
ration of the calcium from the cyanamide, induced by the 
selective absorption of calcium by the soil, and its probable 
precipitation as calcium carbonate. (Seep. 37). The second 
stage is a hydrolysis of cyanamide entirely to urea; the third 
stage is a transformation of urea to ammonium salts. 

II. The cyanamide disappears from the soil solution by two 
processes : 

(a) Absorption and concentration of cyanamide molecules 
in the limiting stratum between the soil solution and the soil 
particles. This takes place during the first few moments of 
contact. (See pp. 37 and 38). 

(b) Removal of the cyanamide molecules from the limiting 
stratum by hydrolysis to urea under conditions of high surface 
pressure and concentration. (See p. 40). 

III. The greatest velocity of hydrolysis occurs when the 



58 CYANAMID MANUFACTURE, CHEMISTRY AND USES 

ratio of soil solution to soil is the least; that is, when the 
liquid film about the soil particles reaches its maximum dis- 
tension, and the cyanamide molecules are in closest contact 
with the soil particles (See p. 42). 

IV. The hydrolysis to urea is brought about in the soil by 
the catalytic action of certain colloidal substances, of which 
the most effective are the hydroxides of manganese and iron, 
and certain natural zeolites (hydrated meta- and tri-silicates 
of aluminium and sodium or calcium (pp. 48-56). Other 
colloids occurring naturally in the soil have less ability of 
transformation. Animal carbon is about as active as soil 

(P- 51). 

V. The soil loses its power of effecting the transformation 
when it is calcined or when it is treated with acids and alkalies ; 
that is, when the colloids are destroyed. Upon addition of 
the colloids again, it reacquires the property of transformation. 

VI. The conversion of cyanamide in sterile conditions is 
entirely to the form of urea. The urea was isolated and iden- 
tified (pp. 43, 44, 50- 

VII. In the hydrolysis of cyanamide to urea, micro-organ- 
isms do not participate, because : 

(a) The transformation proceeds most rapidly at high con- 
centrations of cyanamide and at concentrations far above those 
that support life (pp. 40, 43, and 46). 

(b) The transformation takes place with greatly increased 
velocity at ioo° C. (p. 43). 

(c) The transformation takes place in the presence of anti- 
septics and sterilized materials (pp. 44, 50, and 56). 

VIII. Unless the greatest care is taken to have perfectly 
sterile conditions, the urea is converted into the form of 
ammonium salts. In ordinary soil this change is very rapid 
(pp. 40, 44, and 57). 

IX. The conversion of the urea to ammonium salts hastens 
the hydrolysis of cyanamide to urea by removing the end- 
product of the hydrolysis (p. 57). 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 59 

X. While cyanamide itself is not directly utilized by ordi- 
nary bacteria, this fact is of relatively little importance, since 
the soil bacteria grow in the presence of cyanamide if urea 
or some other nutrient substance is present ; the urea being 
formed by physico-chemical means from the cyanamide. (See 
pp. 34, 36, 44,45. and 57). 

XL The retention by the soil of the nitrogen formed from 
cyanamide is under the form of ammonium salts (p. 45). 



CHAPTER VI. 



Retention of Cyanamid Nitrogen in Soil. 



The absorption and retention of Cyanamid nitrogen by vari- 
ous soil constituents has been investigated by only a few 
workers, and very little has been reported that can be regarded 
as of practical interest. Such tests to be of value should be 
made with natural soils, and not with pure constituents, such 
as ignited glass-sand, as has been done by some investigators. 
The period permitted for absorption should be at least one or 
two days, and the proportion of aqueous solvent should not 
exceed that likely to occur in agricultural practice, nor should 
larger quantities of nitrogen be applied than are likely to be 
used by the farmer. 

The retention of nitrogen is doubtless due to physical pro- 
cesses, as well as to chemical reaction with both the mineral 
and organic constituents of the soil. (See pp. 39 and 45). 
Physically, Cyanamid nitrogen is retained in the soil by pro- 
cesses of absorption in the same way as sodium nitrate, or 
other salts which do not form insoluble compounds by chem- 
ical reaction with the soil. By chemical and biological pro- 
cesses, however, Cyanamid nitrogen is quickly converted to 
the form of ammonium salts, and these are retained in the 
soil in the form of humic and zeolitic compounds of ammo- 
nium. According to, A. D. Hall, the weaker the solutions of 
ammonium salts applied the greater is the percentage of 
ammonium absorbed by the soil. 1 In the field the amount of 
soil is so enormously in excess that the absorption of ammo- 
nium salts is practically complete. 

While plants undoubtedly have the power of directly assimi- 
lating the urea 2 that is formed as a transition product during 
the conversion from cyanamide to ammonium salts, the dura- 
tion of the urea stage is probably very short in the soil, and 

1 A. D. Hall, The Soil, New York, 1910, p. 215. 

2 Jour. Agr. Sci., Vol. IV, Part 3, p. 282. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 6l 

the practical consequences of its brief existence are probably 
very slight. Hutchinson and Miller have shown that ammo- 
nium salts, also, are directly assimilated by plants, 1 but just 
how effective such processes are it is difficult to estimate. 
Practically there can be no doubt but that most of the 
ammonium salts are converted to nitrates prior to their absorp- 
tion by the plant. 

1 Jour. Agr. Sci., Vol. IV, Part 3, p. 2S2. 



CHAPTER VII. 



Nitrification of Cyanamid Nitrogen. 



While some of the fertilizing effect of Cyanamid may be 
due to the presence of urea and ammonium salts, nitrification 
of cyanamide and its decomposition products may take place 
very readily in the soil under favorable conditions, providing 
the concentration of nitrogen is not too great. This is shown 
in an experiment by Wagner, which was carried out as 
follows : a 

Two hundred and fifty grams of sandy-loam soil was mixed 
with 5 grams of marl and the quantity of nitrogen salts shown 
in the table below. Each salt was well mixed with 2 grams of 
gypsum before application in order to facilitate distribution. 
The mixtures were placed in cylindrical glass vessels 6 l /> cm. 
in diameter and 17 cm. high, moistened with 75 cc. water, and 
covered with 50 grams unfertilized earth. The vessels were 
allowed to stand at room temperature and the evaporated 
water was replaced from time to time. After 12, 20, and 33 
days respectively samples were drawn from each series and 
analyzed for nitrate nitrogen. After subtracting the figures 
obtained in the unfertilized control vessels the following 
results were obtained: 

With the sodium nitrate 
Nitrate nitrogen as NO at ioo, the other fertilizers 

(ccm.) gave as nitrate nitrogen 

After After After After After After 

Fertilizer 12 20 33 12 20 33 

application days days days days days days 

0.05 grams nitrogen as 

sodium nitrate 23.7 23.9 24.7 100 100 100 

0.05 grams nitrogen as 
sulphate of am- 
monia 20.8 22.5 — 88 94 — 

0.0125 grams nitrogen 

as Cyanamid 3.9 5.9 5-9 66 99 9^ 

0.025 grams nitrogen 

as Cyanamid 4.1 9.9 II. 2 35 83 91 

0.05 grams nitrogen as 

Cyanamid 0.3 6.3 14.9 1 26 60 

1 Landw. Vers. Stat. Vol. 66, No. 4 and 5, 1907. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 63 

0.0125 grams nitrogen per 250 grams of soil is equivalent 
to a fertilization of about 90 pounds of nitrogen per acre. 
With this large application, even, nitrification of the Cyanamid 
is complete in twenty days. Larger applications require a 
longer period, but are of no practical interest. The above 
results must be considered relatively to each other and not as 
absolute values, since the conditions were probably very favor- 
able to nitrification. 

A similar experiment is reported by Muntz and Nottin. 1 
They found that when 0.25 grams of nitrogen per kilogram of 
soil was used, the relative amount of nitrification in 5 months 
for different fertilizers was as follows: 

Per cent. 

Ammonium sulphate 100 

Calcium cyanamide 88 

Dried blood 66 

Roasted leather 26 

The above fertilization is equivalent to about 450 pounds of 
nitrogen per acre, and has no significance to practical agricul- 
ture. 

When, however, smaller amounts of Cyanamid were applied, 
nitrification was very rapid, and further, the bacteria rapidly 
adjusted themselves to the changed environment and enorm- 
ously increased their ability to nitrify Cyanamid nitrogen, even 
when successively increasing doses were applied. This is 
shown in the following table : 

Amount cyanamid Amount 

nitrogen applied nitrogen present Nitrate nitrogen 

each time at analysis before per kg. of earth 

Date applied grams new application by analysis 

January 17 0.06 — — 

January 26 0.06 0.06 — 

February 7 0.10 0.12 0.01 

March 3 0.12 0.22 0.18 

April 2 0.22 0.34 0.37 

April 25 0.40 0.56 0.58 

May 23 — 0.96 0.81 

1 Annales de l'lnstitut National Agronomique, 2nd Series, Vol. VI, 
No. 1, 1907. 



64 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

The rate of nitrification of Cyanamid is somewhat less than 
that of sulphate of ammonia when both are applied in large 
doses. In doses such as would be used in practical agriculture 
there is probably not much difference. The rate of nitrification 
must vary greatly in different soils and individual experiments 
can show but little of general application. As a general 
average of observations made in Germany, it appears that the 
duration of Cyanamid nitrogen in the soil is about 70-80 days. 
In very active soils it is probably less, in cold soils of low 
bacterial activity it is probably more. Its duration is there- 
fore about midway between that of ammonium sulphate and 
dried blood. 



CHAPTER VIII. 



Toxicity of Fertilizers. 



A review of the numerous agricultural experiments that 
have been reported since 1902, indicates that Cyanamid is not 
equally efficient as a fertilizer in all the conditions in which it 
has been applied. Cases have been noted where there was ap- 
parently an unfavorable action on germination of seeds, unless 
the fertilizer were mixed with the soil several days before the 
seed was sown. It is also said to be poorly adapted for use on 
acid moor soils or on very poor sand soils of low activity. 
Various explanations have been given of the cause of these 
undesirable effects. In some cases the occasional harmful 
action on germination has been attributed to the evolution of 
acetylene from a crude lime-nitrogen containing free calcium 
carbide; in other cases the causticity of the lime has been 
blamed, but usually the unfavorable action on acid moor soils 
or very poor sand soils is charged to the formation of dicyan- 
diamide by the acids in such soils. 

Meaning of "Poison." — It is well to agree at once upon what 
is meant by the term "toxin" or "poison." Dr. Paul Wagner 1 
says "poison, as is known, is a very relative idea, for poisons 
in great dilution are harmless, and non-poisons in great con- 
centrations are harmful." It is obvious that the term "poison" 
could be applied to almost any substance if we do not limit the 
amount which is understood to be used. Unless, therefore, the 
amount which is said to be toxic is distinctly specified, it is 
necessary to assume that the amount used is small and 
popularly regarded as a safe dose. It is also desirable to agree 
upon the amount of injury that can be sustained before the 
effect can be pronounced as harmful. Some substances produce 
temporary exhilaration, followed by serious depression; other 
substances produce temporary depression, but leave the subject 
1 Arbeit, der Deut. Landw. Ges., No. 129, p. 267, 1907. 



66 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

in the long run better than before. Practically, from the stand- 
point of plant physiology, it seems necessary to define a poison 
as a substance which, administered in quantities ordinarily con- 
sidered small, produces functional disturbances ending ulti- 
mately in permanent injury or death. 1 

In this connection it may be well to quote entire the con- 
clusions of Dr. Paul Wagner after seven years of experi- 
menting with lime-nitrogen, both in pot cultures and in the 
field. 2 

CONCLUSIONS OF DR. PAUL WAGNER. 

"i. The statement 'lime nitrogen is a plant poison and must 
be converted by soil bacteria into ammonia and nitric acid in 
order to act as a fertilizer' has led to many faulty conceptions 
and is practically not correct. Poison, as is known, is a very 
relative term, for poisons in great dilution are unharmful, and 
non-poisons in great concentration are harmful. For instance, 
perchlorate occurring in nitrate of soda is a decided poison. 
If one sows 3 kg of perchlorate on a hectare of rye, 
there will be a poisonous action. Chile saltpeter should 
therefore contain not more than one-tenth of a per 
cent, of perchlorate; it should be rejected if it con- 
tains more than 1 per cent, of this poison. Likewise, 
ammonium sulphocyanate is a real plant poison. In the year 
1873, in No. 38 of the Hessian Agricultural Journal, I com- 
municated a marked example of sulphocyanate poisoning. On 
the Rudigheimer estate at Hanau a grain field of 4 hectares 
was poisoned by an application of 100 kilograms of ammonium 
superphosphate with 10 per cent, nitrogen, which later in- 
vestigation showed to contain sulphocyanate. Therefore, this 
extremely slight amount of sulphocyanate was sufficient to 
cause a characteristic poisoning and to decrease the yield to 
about one-third. It has also been learned that ammonium 
sulphocyanate applied a greater or less time before sowing of 

1 See also Pfeffer's Physiology of Plants, Ewart, Vol. II, 258. 

* Arbeit. Deut. L,andw. Ges., Heft 129, 1907, p. 267. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 6j 

the seed, can under certain conditions be decomposed into 
ammonia, so that is no longer poisonous. Nevertheless, the 
sulphocyanates to the extent that they remain undecomposed 
in the soil are decided plant poisons and cannot be applied as 
fertilizers. 

"On the contrary, nitrate of soda, sulphate of ammonia, 
nitrate of ammonia, and carbonate of ammonia contained in 
manure, are known as very favorable nitrogen fertilizers and 
they are still regarded as such, although it is known that under 
certain conditions they can act disadvantageous^. Very con- 
centrated solutions of these nitrogen fertilizers, especially car- 
bonate of ammonia, can, as is evident from our contribution in 
Volume 66 of the Agricultural Experiment Station Reports, 
have a depressing action upon the development of plants, and 
under certain circumstances (which indeed do not occur in 
agricultural practise) they can produce complete destruction 
of the plant. No one, however, designates nitrate of soda, 
sulphate of ammonia or manure as plant poisons. In a 
similar manner it is known that fertilization with quicklime 
must be carried out with great care. Professor Tacke has 
determined by researches upon moor soils a very disadvan- 
tageous action of lime fertilization, and I, and others, have 
found that lime can act harmfully on ordinary soils if the lime 
is applied in too large quantities or at the wrong time. No 
one will, however call quicklime, which is known as a highly 
valuable fertilizer material, a plant poison. 

"In just the same way Cyanamid, or so-called lime 
nitrogen, is to be regarded not as a plant poison, but as a fer- 
tilizer, although it, exactly like quicklime and other fertilizers 
under some conditions, can act harmfully upon the growth of 
plants. Cyanides, sulphocyanates and similar nitrogen com- 
pounds are plant poisons ; they act poisonously in very great 
dilution and cannot serve as fertilizers under any conditions. 
Cyanamid, however, does not belong to this class, for 
this compound can act harmfully or poisonously upon plants 
only in case of very wrong methods of application. 



68 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

"When Prof. Frank requested me six years ago to test 
Cyanamid as to the conditions under which it could be 
used as a fertilizer and its relative fertilizing value, I had 
already been preparing to undertake the test; but I had ex- 
pected, on the ground of observations made with cyanides and 
sulphocyanates, a completely negative result from the experi- 
ments. 

"Our experiments carried out in the laboratory and on small 
experimental plots have not confirmed my previous assump- 
tion. Our field experiments have shown that the application 
of lime nitrogen as a fertilizer was attended with less 
difficulties than one could directly conclude from the experi- 
ments carried out in the laboratory and on small experimental 
plots. Very concentrated solutions of lime nitrogen or ex- 
ceptionally large applications of this fertilizer act harmfully 
upon the plants, as is clearly seen from our pot experiments 
(see page yi and Fig. 5). Under the normal conditions of 
agricultural practice, however, a disadvantageous action does 
not occur, if one follows the directions given for the applica- 
tion of Cyanamid, and these consist essentially in this that the 
lime nitrogen must not be applied in excessive quantities and 
further must not be applied upon acid soils or soils which tend 
to become acid ; that it must be distributed as uniformly as 
possible upon the surface of the field, and must then be worked 
into the ground, when it is not used as a top dresser, by deep 
acting tools, or be plowed under. 

"To illustrate, it should be noted that in our experiments 
(see page 71) an application of 1 gram of nitrogen in the form 
of lime-nitrogen upon 7 kilograms of soil contained in a 
vessel 20 cm. in diameter did not act harmfully, but acted 
favorably from the beginning to the end upon the plant growth 
even when the lime nitrogen was mixed with the soil im- 
mediately before planting of the seed. Upon a circumference 
of 20 cm. diameter, however, one does not apply in agricultural 
practice 1 gram, but only one-tenth or at the highest two-tenths 
of a gram of nitrogen. It is therefore clear that one can 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 69 




uoyoo 

-Ifdcfo fiyi/9U/M9</Z9 
9A/SS90X9 JO UOlCdy 



SJ 



(?uir>^$) u/0^6 j.o PI 9)1 



/O CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

regard the disadvantageous action of lime nitrogen, such as 
happens under applications of exceptionally large quantities in 
pot experiments as either not occurring in agricultural practice 
or as immediately disappearing. Practically, one cannot there- 
fore regard lime nitrogen as a plant poison. It is to be 
regarded as a fertilizer applicable in agricultural practice and 
having a favorable action, although as is necessary with barn 
manure, green fertilizers, bone-meal, horn meal, etc., the nitro- 
gen contained in it must be converted by bacterial activity into 
ammonia and nitric acid in order that it may serve as plant 
food. 

"2. If lime nitrogen is applied in normal quantities, as com- 
pared with other fertilizer materials, distributed as uniformly 
as possible upon the soil, and worked in well with deep-acting 
tools, it exerts no harmful influence even when applied im- 
mediately before sowing of the seed. The idea that lime- 
nitrogen must be completely, or at least to a great extent, 
converted into ammonia or nitric acid before it comes into con- 
tact with the seed is wrong, although it is possible that the action 
of lime nitrogen in many cases can be increased if it is applied 
8 or 14 days before sowing of the seed. 

"3. Lime nitrogen in ordinary field practice can act harm- 
fully only when conditions are such that a part of the calcium 
cyanamide suffers an unnormal decomposition. Conditions 
under which this can happen are present especially in acid moor 
soils or in soils which tend to become acid, or soils very rich in 
humus, and therefore very poor in lime. It is known that 
moor soils acts otherwise than normal towards other nitrogen 
fertilizers as well. Sulphate of ammonia has an unfavorable 
action upon acid soils. In order to avoid these unfavorable 
conditions of acid soils previous liming is necessary. 

"4. Like all organic nitrogen fertilizers, green substances, 
barn manure, horn meal, etc., the conversion into ammonia and 
nitric acid is necessary in order to yield nitrogen assimilable 
by plants, and like ammonia (although many plants take it up 
and use it as such), for most plants it has its full effect only 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES Jl 

when it is converted into nitric acid ; so the nitrogen of the 
lime-nitrogen must be converted into ammonia and nitric 
acid before it will yield nitrogen that the plants can assimilate. 
"5. It is known that the conversion of Cyanamid and the 
organic forms of nitrogen into ammonia and nitric acid is 
brought about by the activity of certain soil bacteria and that 
this conversion, according to the special activity of the soil, 
sometimes proceeds more rapidly and sometimes more slowly. 
Upon so-called medium soils in good condition the organic 
fertilizers as a rule act more completely than upon light dry 
sandy soils or upon heavy clay soils. The medium loam soils 
in good condition seem to offer comparatively the best con- 
ditions for the action of lime nitrogen. Whether the con- 
version of calcium cyanamide into ammonia proceeds by an 
intermediate formation of urea is unproved." 

The above was written by Dr. Wagner before the mechanism 
of the conversion of Cyanamid in the soil had been worked 
out. These later researches show that the conversion is both 
physico-chemical and biological, as has been set forth in 
Chapter V. 

The experiments on the effect of concentration to which 
Dr. Wagner refers were made in vegetation pots with a 
variety of nitrogenous compounds, on various types of soil, 
and with various crops. All the results point to the same 
general conclusion, which is illustrated in Fig. 5. This test 
was made with oats planted on a sandy-loam soil, in pots 
20 cm. high and 20 cm. in diameter. The seed was planted 
on the day of fertilizing, May 9, 1905, and the grain harvested 
on July 14, 1905. The lime-nitrogen contained 20.06 per cent, 
nitrogen, and the calcium nitrate (commercial grade) con- 
tained 11.65 P er cen t. nitrogen. 1 The yields of grain are 
plotted against the amounts of nitrogen applied to the soil 

(Fig- 5). 
Each of these curves is an illustration of the Law of 

Diminishing Returns. For the smaller applications of nitro- 
1 Landw. Vers. Stat., 66, IV-V (1907), p. 346. 
6 



J2 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

gen, the increased yield is almost proportional to the amount 
of nitrogen applied, but the rate of increase drops off rapidly 
until a point is reached where further applications not only 
do not increase the yield but tend to decrease it. If too much 
fertilizer is applied the plant may even be killed. The "burn- 
ing" and occasional destruction of vegetation by excessive 
applications of fertilizer salts is well known to agriculturists. 
A similar phenomenon has been investigated by Headden and 
Sackett 1 in Colorado, where it was shown that the formation 
of excessive quantities of nitrates has caused in some cases 
the total destruction of all plant life, often over areas miles 
in extent. 

Toxicity, therefore, is a question of the amount of fertilizer 
applied. All of the common, nitrogenous, mineral fertilizers 
may have a toxic action if too much is used, but with the 
ordinary applications of practical agriculture none of these 
materials is toxic. Experience has determined the maximum 
quantities of nitrogen that can be economically utilized by the 
various crops under various soil conditions, and the possible 
effects of larger quantities than this maximum economical 
quantity in each case have little interest to the practical farmer. 
Cotton, corn, wheat, oats, and similar crops seldom economically 
utilize more than 15 to 25 pounds of nitrogen per acre. Sugar 
beets and sugar cane may utilize as high as 40 to 50 pounds. 
Potatoes, truck crops, some fruits, and tobacco may utilize as 
high as 60 to 70 pounds of nitrogen per acre. With such 
applications it is doubtful if any of the mineral fertilizers in 
question would exert a toxic action on the plant, even if they 
were applied alone, provided the time and method of applica- 
tion were suitable. 

As a matter of fact, however, when large applications of 

nitrogen are desired, it is customary to mix several kinds of 

nitrogenous materials together and to apply the mixture in 

several portions, instead of all at one time. Moreover, agri- 

1 Colorado Exp. Sta. Bulletiu 179, 191 1. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES /3 

cultural experience has shown that nitrogenous fertilizers are 
not utilized as economically when applied alone as when they 
are used in conjunction with phosphates and potash salts; the 
presence of phosphorus and potassium seems to greatly modify 
the ability of the plant to assimilate nitrogen. As a general 
rule, it is seldom, indeed, that more than 25 pounds of nitro- 
gen, derived from a single source, is applied at one time, 
unaccompanied by phosphates and potash. In normal agri- 
cultural practice, therefore, the question of toxicity of the 
common nitrogenous fertilizers may be disregarded. If the 
farmer wishes to depart from the normal practice, it is usually 
best to follow the instructions issued by fertilizer manufac- 
turers for the use of their products. Such instructions usually 
designate 20 to 25 pounds of nitrogen per acre as the maximum 
application, and recommend that the material be applied during 
the preparation of the soil a week or more before the seed 
is sown. They also caution against the danger of direct 
contact of the undiluted fertilizer with the leaves or roots of 
the plant. 

OTHER EXPLANATIONS OF TOXIC ACTION. 

Whether or not acetylene, which may be generated by the 
action of moisture on a lime-nitrogen containing calcium car- 
bide, is harmful to plant life, is of little interest to the 
Cyanamid industry, since the material prepared for use as a 
fertilizer does not contain calcium carbide. The lime-nitrogen 
made in Europe in former years, sometimes contained slight 
amounts of carbide but it is extremely doubtful if there were 
any harmful effects from this ingredient. H. Kappen 1 and 
E. Haselhoff 2 claim that they could observe no harmful effects 
of acetylene on plant growth. No reports have been found 
which show that acetylene may be harmful. 

The free lime in the German "kalkstickstoff" or lime- 
nitrogen is in the form of calcium oxide, while in the Ameri- 

1 Fuhling's Landw. Zeit, Apr. 1908, 286. 

2 Landw. Vers, stat., 68, 1908, Nos. 3 and 4. 



74 CYAN AMID — MANUFAC CHEMISTRY AND USES 

is the i ■ of calcium hydroxide and 

. . »cts of the lime in either form upon plant 

:". - .r'.y by Wagner in the extract quoted 

ie anion::: : ... calcium in Cyananiid. ex- 

... 5 about 55 ied 

to the s s ne :essarily lim ted : E nitrog 

an hardly reach such an amount that it 
1th plant g 
regard to the on of Cyananiid on 

es that the same 

a - mium sulphate, and that the bad effects 

the a i ma - 

to aj E the Eertilizer. Soils which are acid 

is rule unfit for : igr :ulture, and should be 

ato g - judicious liming. Fer- 

le harmful ^uc;:? of 

dons stitute the limiting factor in 

a a . nditions must . :or- 

recte f .mamid, 

O.ould not be ap: soils with the 

ex:. _ rofit unless : . unfavorable con- 

tions > liming The quantity of 

Cyana 2 of some assisl - nsufifi- 

-. which require Erequently as much 

tons slaked lime in them to 

anamid on -. I soils has 

uted to the possible formation of dicyan- 

r.anamide. That there is no chem- 

sis for this ill be shown 

DICYA^-DIAXTDE. 

..ndiamid: :::uch discussed in 

ture tt - ssary, in order 

il understa g El • - xt i rom the mass 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 75 

of experimental data that have been reported the results that 
are consistent with all the known facts, and then to reconcile 
the apparent disagreements with the consistent facts. 

Formation. — The researches of Ulpiani 1 show without doubt 
that acids do not determine the formation of dicyandiamide 
from calcium cyanamide. Acids acting on calcium cyana- 
mide produce calcium salts and free cyanamide. By the 
further action of the acids, from the weakest to the strongest, 
there is formed first urea, and secondly, especially in the case 
of weak acids, ammonium salts. (See also p. 12). F. 
Lohnis and R. Moll 2 found that even humic acid, in excess, 
acting upon lime-nitrogen for 8 days at 40° C. produced not 
the slightest trace of dicyandiamide. There is no evidence of 
any kind to show that acids ever produce dicyandiamide from 
cyanamide. Neither do strong alkalies produce dicyandiamide, 
but always produce urea and free ammonia. Weak alkalies, 
however, and especially calcium hydroxide, readily effect the 
polymerization, although in this case also there is formed con- 
siderable urea. The formation of dicyandiamide in lime- 
nitrogen is brought about by the combined action of moisture, 
which causes the hydrolysis of calcium cyanamide to cyan- 
amide, and lime which determines its polymerization to dicyan- 
diamide. These reactions take place at ordinary temperatures 
very slowly, as shown below, but proceed very rapidly above 
yo° C. At about 100 9 C. other reactions begin with formation 
of ammonia and small amounts of other derivatives. Water 
and heat alone do not cause the polymerization to dicyandi- 
amide; Ulpiani boiled a pure solution of cyanamide 50 hours 
without any change. 3 

Decomposition. — In a solution of lime-nitrogen, dicyan- 
diamide forms and decomposes simultaneously. This is seen 

1 Gaz. Chim. Ital., 1908, II, No. 4, 358.417. 

? Centl. Bakt. XXII, 276. 

'■'' Rend. Soc. Chim. di Roma. p. 4 1906. 



/6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

in the following table by G. Liberi, 1 showing the content of 
cyanamide and dicyandiamide nitrogen in solutions of lime- 
nitrogen made by extracting with cold water and filtering and 
maintaining at 27 ° C. The figures are given as percentages 
of the original lime-nitrogen. 

Dilute solution i per cent, lime Concentrated solution 5 per cent, 
nitrogen • lime nitrogen 



Time elapsed 
in days 


Nitrogen as 
cyanamide 
per cent. 


Nitrogen as 

dicyandiamide 

percent. 


Nitrogen as 

cyanamide 

per cent. 


Nitrogen as 

dicyandiamide 

per cent. 


O 


18.63 


— 


18.63 


— 


I 


16.38 


O.46 


14.56 


O.70 


2 


14.42 


O.56 


II.76 


i-54 


6 


12.74 


O.62 


9.IO 


2.84 


II 


I0.22 


O.50 


5.18 


2.24 


18 


7.42 


o-39 


i-75 


1.71 


31 


3.OI 


0.38 


0.00 


1-25 


45 


O.OO 


o.34 


— 


0.84 


58 


— 


0.28 


— 


o.53 


76 


— 


0.22 


— 


0.23 



The maximum amount of dicyandiamide occurs in each case 
at the end of 6 days' standing. The decomposition of the 
dicyandiamide is very slow, as is seen in the concentrated 
solution after the 31st day, when all the Cyanamid has been 
removed, and no more dicyandiamide can form. Its rate of 
formation is somewhat faster, and is undoubtedly determined 
by the concentration of both nitrogen and calcium. The per- 
centage of the total nitrogen transformed to dicyandiamide 
is about five times as great in the concentrated as in the dilute 
solution. With the removal of the cyanamide it was observed 
that crystals of pure calcium hydroxide settled out on the 
walls of the vessel. 

The rapid disappearance of the cyanamide shows that the 
formation of other derivatives of cyanamide in this solution is 
much more rapid than the formation and decomposition of 
dicyandiamide, and it is therefore evident that most of the 
cyanamide decomposes directly to these other derivatives, and 
not through the dicyandiamide form. The largest part of 
1 Annali Staz Chim. Agrar. Sper di Roma Series II, V, 191 1. 



CYANAMID MANUFACTURE;, CHEMISTRY AND USES JJ 

these other derivatives is urea, and the balance is amidodi- 
eyanic acid, melamine and ammeline. (See also p. 29). 

Conversion in Soil. — The chemical behavior of dicyandiamide 
in the soil has not been studied in the thorough manner in 
which that of cyanamide has been studied, and much of the 
data at hand is invalidated by the fact that enormous quanti- 
ties of nitrogen were used. It is necessary to draw our con- 
clusions solely from the vegetation tests that have been 
reported. 

A review of these culture tests will show that they fall into 
two classes ; one, in which chemically pure dicyandiamide was 
used, and the other in which home-made dicyandiamide was 
used. 

Among the prominent investigators who used pure dicyan- 
diamide are Wagner, Kappen, Sabaschinkoff, Lohnis, Brioux, 
and C. J. Milo. Their results show that chemically pure 
dicyandiamide has practically no fertilizing value but 
on the other hand may have slight toxic action if more 
than 45 pounds of dicyandiamide nitrogen per acre is applied. 
The results are in such agreement that it will not be necessary 
to quote them here. Among those who used dicyandiamide 
prepared in their own laboratories are Perotti, Ulpiani, R. 
Inouye and K. Aso. They found that home-made dicyandia- 
mide has a fertilizing value equal to that of ammonium sul- 
phate provided it is not used in quantities exceeding 100 
pounds of nitrogen per acre. 

Perotti, 1 for instance, in pot tests with wheat, grown to 
maturity, obtained the maximum crop with 75 pounds of nitro- 
gen per acre in the form of home-made dicyandiamide. The 
increase in yield over the control pot without nitrogen was 
about 100 per cent. With buckwheat the maximum crop was 
obtained with 150 pounds of nitrogen per acre, and the in- 
crease in yield was about 200 per cent. With flax the maximum 
yield was with 300 pounds of nitrogen, and the increase in 
yield was about 60 per cent. 
1 Cent. Bakt. XVIII, 55, 1907- 



Pounds nitrogen 

from 
ammou. sulphate 


Pounds nitrogen 

from 
dicyandiamide 


Average \ 

of one p 

green rape. 


— 


— 


5-o 


240 
160 


80 


59-4 
62.6 


160 


80 


64.0 


— 


240 


8.4 



78 CYAN AM ID — MANUFACTURE, CHEMISTRY AND USES 

R. Inouye 1 made pot tests with rape and barley, fertilizing 
with a dicyandiamide made by himself from lime-nitrogen, and 
and analyzing 46.7 per cent, nitrogen. The rate of fertiliza- 
tion was equivalent to 2,400 pounds superphosphate per acre, 
1,200 pounds potassium carbonate and the amounts of nitrogen 
shown in the table below, which gives also the yield obtained : 

it Average weight 

of one plant 
green rape. Grams air-dry, barley. Grams 

1.8 
8-3 
9.0 
9.0 
2-5 

The dicyandiamide in the fourth pot was applied as a top- 
dressing. Although the fertilization was very heavy there is 
no doubt that the results are very good when 80 pounds of 
nitrogen from impure dicyandiamide is used with ammonium 
sulphate, although 240 pounds of nitrogen from dicyandiamide 
alone is little better than no fertilizer. This is clearly an ex- 
cessive amount of dicyandiamide. 

K. Aso 2 made some toxicity tests with a dicyandiamide 
made by himself from lime-nitrogen, and analyzing 59.88 per 
cent, nitrogen. Buckwheat and oat plants were grown to a 
height of about 10 cm. in ordinary soil and were then trans- 
ferred to flasks containing solutions of different concentrations 
of dicyandiamide. When the solutions contained less than 
0.01 per cent, of nitrogen from dicyandiamide the plants con- 
tinued growing normally and developed better than in the 
control flasks. When larger concentrations were used the 
plants showed the characteristic effects of dicyandiamide 
poisoning; that is, for increasing doses, first, appearance of a 
brown color on the tips of the leaves, then drying of the tips, 
although usually followed by recovery and increased growth ; 
finally, with very large concentrations, curling and drying up 
of the leaves and destruction of the plant. Here, as with 

1 Jour. Coll. Agr. Imp. Univ. Tokyo, Vol. I, No. 2, 1909, p. 193. 

2 Jour. Coll. Agr. Imp. Univ. Tokyo, Vol. i, No. 2, 1909, p. 211. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES /9 

Cyanamid and other fertilizers, toxicity is a question of con- 
centration, although the specific toxicity of pure dicyandiamide 
is considerably larger than that of impure dicyandiamide. 

Some tests were also made with rice transplanted to field 
plots (0.83 qm.) manured alike with superphosphate, potassium 
carbonate and nitrogen compounds at the rate of 90 pounds 
per acre each of phosphoric anhydride, potash and nitrogen 
(except control). The nitrogenous substances were am- 
monium sulphate containing 21.2 per cent, nitrogen, lime-nitro- 
gen with 12.47 P er cent - nitrogen, and dicyandiamide with 46.7 
per cent, nitrogen. They were applied at different periods be- 
fore the transplanting of the rice clumps. The total weight 
in grams of the plants obtained in the air dried state were : 

Fertilized days before planting 

Fertilized with o 7 14 21 28 35 

No manure 229 — — 

No nitrogen 436 — 

Ammonium sulphate • • 764 — — — 

Lime-nitrogen 614 767 7S6 807 788 744 

Dicyandiamide 507 575 572 670 652 609 

The yield of clean grain was as follows : 

Fertilized days before planting 



Fertilized with 





7 


14 


21 


28 


35 




• 75 
149 














— 


— 


— 


— 








Ammonium sulphate.. 


266 












Lime-nitrogen 


197 


259 


260 


258 


280 


257 




■ 183 


20S 


209 


238 


244 


239 



This experiment shows a somewhat lower result with lime- 
nitrogen than with ammonium sulphate applied at the time of 
planting, but a somewhat larger yield when the lime-nitrogen is 
applied 7 days before planting. The dicyandiamide is more 
effective when applied two or three weeks before planting than 
when applied at the planting, but it is never as effective as 
the ammonium sulphate, being at the best about 89 per cent, 
as effective in producing grain. In the cultivation of rice in 
America the maximum utilizable application of nitrogen does 



80 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

not exceed 10 pounds per acre. Hence, the above quantities 
are many times larger than any met in agricultural practice. 

A similar experiment was made in pots containing 8 kg. of 
soil, manured with double superphosphate, potassium sulphate 
and nitrogen at the rate of 120 pounds of P 2 5 , K^O and N per 
acre respectively. The lime-nitrogen contained 11.8 per cent. 
N and the dicyandiamide 59.9 per cent .N. The yields in grams 
of air-dry plants were as follows : 

Fertilized days before planting 

Fertilized with o 7 14 21 

Ammonium sulphate •••67.5 — — — 

Lime-nitrogen 65.6 69.6 70.6 74.8 

Dicyandiamide 66.6 74.3 73.8 71.5 

The yields of grain were : 

Fertilized days before planting 

Fertilized with o 7 14 21 

Ammonium sulphate • • • 29.5 

Lime-nitrogen 28.3 30.0 29.5 33.2 

Dicyandiamide 30.5 33.5 31.7 33.7 

In this experiment the highest results were obtained with 

dicyandiamide applied a week before planting. When applied 

at the time of planting the results are about the same as those 

with ammonium sulphate. 

PURE SUBSTANCES AND TOXICITY. 

There are several observations reported in the literature that 
may help us to understand why a chemically pure dicyandia- 
mide should be toxic, while an impure dicyandiamide may have 
a fertilizing value equal to that of ammonium sulphate. 

It has been noted by Sabaschnikoff 1 that a fertilization with 
chemically pure calcium cyanamide, in comparison with lime- 
nitrogen containing the same amount of nitrogen, gives only 
from one-third to one-half as large an increase in yield as is 
obtained from the lime-nitrogen, both being applied under 
exactly the same conditions. 

C. J. Milo 2 made some experiments on sugar cane, in which 

1 Mitt. Landw. Inst., Univ. Leipzig, Vol. IX 1908, p. 106. 

2 Archief voor de Suikerindustrie in Nederlandsch-Indie, 20, 482-539. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 8l 

the sugar cane, in baskets, was watered one month and two 
months respectively after planting, with solutions of lime- 
nitrogen (6 per cent, calcium carbide), pure cyanamide, 
CN.NHo, basic calcium cyanamide, urea and dicyandiamide. 
The solutions contained each an amount of nitrogen equivalent 
to an application of 75 pounds per acre. The pure cyanamide 
proved very toxic and two out of three plants were killed after 
the second application. About two weeks after the second 
application, probably when the cyanamide had been converted 
to other forms, the remaining plants in this basket began to 
grow luxuriantly. The basic calcium cyanamide caused the 
plants to look sick temporarily, and they remained inferior. 
The dicyandiamide (98.5 per cent, pure) was not as intense 
in its action as pure cyanamide, causing no destruction, but 
the bad effects lasted longer than those of pure cyanamide, and 
the plant seemed to lack nitrogen nourishment. The urea 
caused luxuriant growth from the time of application, and was 
slightly better than the sulphate of ammonia and lime-nitrogen 
applications. The lime-nitrogen and sulphate of ammonia 
solutions produced full grozvth and zvere equally effective. 

It appears therefore, that the fertilizing value of lime- 
nitrogen, decidedly can not be judged from the fertilizing 
action of pure cyanamide or pure calcium cyanamide, and that 
the fertilizing value of impure dicyandiamide is quite different 
from the fertilizing value of pure dicyandiamide. It seems 
that the plant is unable to utilize these pure compounds of 
nitrogen, but that in lime-nitrogen there are some substances 
that neutralize such toxic compounds, or help remove them, or 
that act upon the plant in such a way as to enable it to with- 
stand the toxic properties until they are destroyed by the con- 
version of the cyanamide and its polymers by the catalytic 
action of the soil. It is quite possible for instance, that the 
lime and the extremely finely divided carbon in lime-nitrogen 
may play a part in the rapid decomposition of the cyanamide. 
It is also possible that the urea, and other derivatives that are 
so easily formed from cyanamide, furnish the plant with 



82 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

nourishment that enables it to withstand otherwise toxic effects 
that might check growth if such nourishment were not avail- 
able (see also page 34). 

Conclusion. — Toxicity of Cyanamid is simply a question of 
concentration. Under normal soil conditions and with the 
normal applications of practical agriculture there are no un- 
usual effects on the germination of the seed or on the growth 
of the plant. This is verified constantly in the extensive use 
of Cyanamid in agriculture. 



CHAPTER IX. 



Agricultural Use of Cyanamid. 



Fertilizer Tests.— In the selection of the most economical 
fertilizer it is necessary to consider, among other things, the 
nature of the crop, the qualities desired in the plant grown, 
the type of soil, the effect of long-continued use of the fer- 
tilizer, the cost and the relative yields. Thus, the rice-plant 
seems to be unable to assimilate nitrates easily, but readily 
assimilates ammonium compounds. 1 The quickly acting 
forms of nitrogen usually produce rank, heavy growth 
of the green parts of the plant, with little fiber, while 
the slowly acting forms produce thinner leaves, and stems 
with greater strength. For forcing purposes, the nitrates are 
ideal ; for slow, steady growth, the organic forms of nitrogen, 
Cyanamid, ammonium sulphate, etc., are to be preferred. Soil 
conditions are often a determining factor. Thus, loose, open 
soils in regions that receive a great deal of rain do not readily 
retain nitrates. Soils of low lime content may become acid 
by the addition of ammonium sulphate year after year: the 
sulphate radical enters into combination with the lime of the 
soil and carries away the calcium in the drainage waters. 2 
Very acid soils are not economically fertilized with substances 
like Cyanamid, ammonium sulphate and other materials requir- 
ing nitrification, since nitrifying bacteria are notably deficient 
in acid soils, especially acid sandy soils. Such soils should be 
put into productive condition by proper judicious liming, some 
time previous to the fertilization. On light, sandy soils where 
heavy liming may damage the crop the yearly addition of a 
small amount of lime as a part of the fertilizer is of great 
assistance in overcoming the tendency towards acidity. The 
relative yields per unit of money invested in the different fer- 
tilizers is often the controlling factor in their selection, but 

1 Hawaiian Agr. Exp. Sta. Bulletin 24. 

2 A. D. Hall, Fertilizers and Manures, p. 62, 1909. 



84 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

since prices vary, it is customary to express the yields on 
the basis of equal applications of nitrogen. 

There is therefore a large number of factors that affect the 
selection of the most economical fertilizers. The statistical 
method of merely averaging the yields of a large number of 
experiments regardless of their character, does not give very 
much practical information. The errors of experimentation 
with Cyanamid are usually in one direction, and hence do 
not offset one another. One of the most common errors is 
the use of quantities of nitrogen far in excess of what would 
be applied in practical agriculture, as indicated on page 69. 
It is shown in Fig. 5 that the relative efficiency of utilization, 
of the nitrogen in various compounds is not the same at all 
applications. The relative values at an application of 1 gram 
per pot are entirely different from the relative values at 0.5 
grams, or at lower applications. Moreover, the order of 
superiority may be different at different applications, as shown 
on the calcium nitrate curve. At the lower concentrations, 
such as obtain in practical agriculture, under favorable 
soil conditions, all of the common nitrogenous mineral 
fertilizers have about the same efficiency of utilization, 
in this experiment. Not only is it a mistake to assume that 
results obtained at one concentration will hold true for other 
concentrations, but it is. of course, equally wrong to assume 
that an average of the results at various concentrations will 
hold true for a particular concentration. The relative effi- 
ciencies also vary with the nature of the soil and with the 
crop. Results obtained on sand may not hold on clay, and 
vice versa. Acid soils may act differently from neutral or 
alkaline soils. A nitrogenous fertilizer applied alone usually 
gives entirely different results when mixed with other nitro- 
genous fertilizers, or with phosphates, acid or basic, or with 
potash salts. 

A source of error that has probably vitiated many of the 
reported experiments is the readiness with which unhydrated 
lime-nitrogen changes in weight, by absorption of moisture 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 85 

and carbon dioxide, especially when stored in small quantities. 
It is possible that a great many investigators have purchased 
lime-nitrogen at a certain analysis, have allowed the material 
to remain exposed to the atmosphere several months, and 
have then weighed out the fertilizer for the test, assuming that 
its analysis is practically the same as when it was bought. 
The error introduced by the weighing up of the fertilizer one 
month after analysis may amount to 5 to 8 per cent, of the 
total nitrogen, in the case of a single bag exposed in a damp 
climate. In America, where the Cyanamid is completely 
hydrated, the error is much less (see p. 27), but it is 
still large enough to make it desirable to have the fer- 
tilizer weighed out shortly after the analysis is determined. 

Another error is the application of Cyanamid only a short 
time before the harvest. Since Cyanamid may take 70 to 80 
days 1 to be completely utilized, it is obvious that the maximum 
efficiency is obtained only when the application is made not 
less than 70 to 80 days before the harvest. 

The main purpose of a fertilizer test is to determine the rela- 
tive profits that can be made by the use of different fertilizers. 
In view of the difficulties of experimentation, and the danger 
of drawing unwarranted conclusions from insufficient or 
irrelavant data, as pointed out above, probably the only fair 
test of a fertilizer is obtained zvhen it is applied under the con- 
ditions that prevail where the consumer uses it. All other 
methods require special proof that the results obtained experi- 
mentally would also be obtained practically, and such proof 
is not always available. 

To illustrate the considerable variation in the results 
obtained with different materials in different conditions, a few 
of the results of prominent investigators are give here. Thus, 
Strohmer, with sugar beets, obtained as an average of 7 fields, 
100 pounds of sugar when sodium nitrate was used, to 104 

1 Dr. A. Frank, private communication. 



86 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

pounds of sugar when lime-nitrogen was used. 1 J. Kloppel 2 
obtained yields of sugar beets with no fertilizer, sodium nitrate 
and lime-nitrogen respectively of ioo, 127, and 149, while the 
yields of sugar were 100, 99, and 130. As an average of 10 
cereal and root crops in 29 field experiments, Steglich 3 assigned 
the following values to the various materials : no fertilizer, 81 ; 
sodium nitrate, 100; ammonium sulphate, 95; and lime-nitro- 
gen, 96. Schneidewind, 4 as an average of 5 cereal and root 
crops reports that the increase in yield over the fields un- 
fertilized with nitrogen were comparatively, sodium nitrate, 
100; ammonium sulphate, 88; and lime-nitrogen, 73. Wagner, 
Director of the Experiment Station at Darmstadt, 5 as a sum- 
mary of 11 field tests on cereals with 27 pounds or less of 
nitrogen per acre, reports the increased yield over the fields 
without nitrogenous fertilizer, comparatively as follows : 
Sodium nitrate, 100; ammonium sulphate, 87; and lime-nitro- 
gen, 94. Miintz and Nottin, as an average of 11 field tests 
with wheat report the following comparative yields obtained: 
Cyanamid, 100; ammonium sulphate, 94; dried blood, 96. ° 

USE AS A WEED DESTROYER. 

In Germany, lime-nitrogen is used to a considerable extent 
for the destruction of obnoxious weeds, such as wild mustard, 
occurring in grain crops, particularly oats. The fine, dry, lime- 
nitrogen is scattered either by hand or by machine early in the 
morning when the leaves are wet with dew, or after a rain, at 
the rate of 60 to 90 pounds per acre. The lime-nitrogen readily 
clings to the rough, hairy, almost horizontal leaves of the wild 
mustard, and forms a concentrated solution in the moisture on 
the leaves. This tends to dilute itself by osmosis and brings 

1 Oesterr-Ungar., Zeit. fur Zuckerindustrie und Landwirtschaft, 
XXXV, No. VI, 1906, 676. 

2 Fuhling's Landw. Zeit., 56, No. 15, 1907, p. 539. 

3 Fuhling's Landw. Zeit., 56, No. 22, 1907, p. 780. 

4 Arbeit. Deut. Landw. Ges., No. 146, 1908, p. 116. 

5 Arbeit. Deut. Landw. Ges., No. 129, 1907. 

6 Annales de l'lnstitut National Agronomique, 2nd Series, Vol. VI, 
No. 1. See also pp. 45-47- 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 87 

about the destruction of the mustard within a few days. The 
application is made when the mustard plant is young, best 
when it has only four or six leaves. The more leaves it has 
the more lime-nitrogen will be required. The grain crop may 
be affected a little immediately after the application, and may 
turn somewhat brown at the tips of the leaves, but it will 
quickly recover and become much greener than the grain in 
untreated fields. The leaves of the grain crops, especially oats, 
stand almost vertical and are comparatively smooth and waxy, 
so that very little lime-nitrogen clings to them and no 
permanent damage is done. Practically, this method of de- 
stroying wild mustard is quite economical, since the nitrogen 
applied in this way seems to have as full fertilizing effect as 
if it were applied under the crop. The mustard, on the other 
hand, is practically eradicated. 

DIRECTIONS FOR APPLICATION AS FERTILIZER. 

Very little of the Cyanamid made in this country is applied 
alone, practically all of it being used as a part of mixed 
fertilizers. For the guidance of those who wish to use it with- 
out admixture with other materials, the following suggestions 
are offered, although it should be recognized that a true test 
of the efficiency of the Cyanamid used in this country is made 
only under the conditions in which it is usually applied, that 
is, as a part of a mixture containing phosphoric acid, potash, 
and frequently other forms of nitrogen. 

Cyanamid is least efficient when applied as a top-dressing. 
This is probably due to the quick reaction and fixation in the 
soil, so that much of the nitrogen is retained in the upper 
layers of soil where the plant roots do not reach it readily. 
The application should be made in such a way that the 
Cyanamid will be buried about where the plant roots are 
expected to grow. It should be scattered through the lower 
layers of cultivated soil as much as possible, so as to favor the 
greatest spreading of the roots. In the event of a dry season, 
the larger the root system, the better will be the ability of the 



88 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

plant to withstand drouth. Dropping the fertilizer in narrow 
rows favors the development of bunched root systems, which 
will do very well as long as the supply of fertilizer lasts and 
the water supply is good, but are insufficient for the demands 
of the plant in dry weather. If the application is large broad- 
casting one-half or two-thirds of the fertilizer before plowing, 
or after plowing and before harrowing, with the application of 
the remainder in the row before seeding, or along the row 
after the plants are up, will be found to produce the best 
results. Care should be taken that the fertilizer is well mixed 
with the soil and that pure fertilizer and seed are not in direct 
contact, thereby avoiding the so-called "burning" of young 
plants. When the fertilizer is applied alongside the rows after 
the plants are up, it should be well worked in with the cultiva- 
tor or with hoes. Care should be taken not to get highly con- 
centrated fertilizers on the leaves of the plant, especially if the 
plant is wet. Since Cyanamid is a medium-slow-acting fer- 
tilizer, it should be applied to the crop not less than 70 to 80 
days before the harvest, in order that the nitrogen may be 
completely utilized by that crop. 

The quantity of Cyanamid that can be economically applied 
at one time is preferably limited to 150 pounds per acre. 
Experience has shown that the most economical utilization 
of a nitrogenous fertilizer is obtained when it is used in con- 
junction with the other fertilizing elements, phosphorus and 
potassium. For this reason, it is recommended that Cyanamid 
be used as a part of a fertilizer mixture, rather than that it 
be applied alone. 

If Cyanamid is to be applied to very acid soils, such soils 
should be put in productive condition by thorough judicious 
liming some time before the application of the fertilizer. The 
application of barnyard manure will help to establish the 
bacteria that are deficient in such soils. 

When Cyanamid is applied alone, better results will be ob- 
tained if it is applied several days before the seed is sown, 
especially if the applications are large. For small applications, 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 89 

when care is taken to mix the fertilizer well with the soil, the 
seed may be planted directly after the fertilizer is spread. 
Even distribution of the Cyanamid is facilitated by previously 
mixing it with two to three times its weight of damp earth. 

USE OF COMPLETE FERTILIZER MIXTURES. 

Since most of the Cyanamid used in this country comes to 
the farmer as an ingredient of mixed fertilizers, it is as a rule 
not necessary to have special instructions for its use. From 
the known chemistry of calcium cyanamide it is very probable 
that when Cyanamid is mixed with acid phosphate, the phos- 
phoric acid causes a considerable conversion of Cyanamid 
nitrogen to the form of urea, (page 12). At any rate, the ordi- 
nary practice in the use of mixed fertilizers is such that the 
presence of Cyanamid nitrogen will not require any modifica- 
tion of the usual practice. 



CHAPTER X. 



Making Fertilizer Mixtures with Cyanamid. 



MIXTURES WITH AMMONIUM SALTS. 

Cyanamid contains about 55 per cent. CaO, of which about 
30 per cent, is present as CaCN„, 21 per cent, as Ca(OH) 2 , 
and 4 per cent, as CaC0 3 and other forms. Most of the 
calcium, therefore, dissociates readily and can react when 
brought into contact with certain bodies. In the presence of 
ammonium sulphate for instance, a double decomposition takes 
place as follows: 

Ca(OH) 2 + (NH 4 ) 2 S0 4 — CaSO, + 2 NH 3 + 2 H 2 0. 

Hence, if Cyanamid and ammonium sulphate are mixed 
alone there will be a large loss of ammonia. The same kind 
of reaction takes place with other ammonium salts. 

If, however, as is practically always the case, there is 
present an adequate amount of acid phosphate or other acid 
material, the acid of the acid phosphate immediately fixes the 
free ammonia and prevents its escape. The ammonia is com- 
bined probably as ammonium phosphate or as calcium ammo- 
nium phosphates, or both. To prevent loss of ammonia, there- 
fore, it is only necessary to have a sufficient amount of acid 
material present so that the resulting mixture will be acid in 
reaction. This condition is obtained when the amount of 
Cyanamid does not exceed 100 pounds of powdered Cyanamid 
or 200 pounds of granulated Cyanamid per 800 pounds of 
ordinary acid phosphate containing 14 or 16 per cent, of 
available phosphoric acid. Such mixtures have been tested 
in practical fertilizer manufacturing and show no losses of 
ammonia. The quantity of ammonium sulphate present is 
practically immaterial. Acid fish contains some nitrogen as 
ammonium sulphate, and should be mixed in accordance with 
the above rule. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 91 

MIXTURES WITH ACID PHOSPHATE. 

In ordinary acid phosphate analyzing 16 per cent, available 
phosphoric acid, there is usually found about 5 per cent, as 
free phosphoric acid, 9 per cent, as mono-calcium phosphate, 
and 2 per cent, as di-calcium phosphate. When such a phos- 
phate is mixed with Cyanamid there is obviously a neutraliza- 
tion of free acid, and of acid hydrogen of the mono- and di- 
calcium phosphate, the extent of the reaction depending upon 
the amount of active lime introduced by the Cyanamid. The 
neutralization is, of course, attended by evolution of heat, 
and this heat is the cause of the unfavorable results of mixing 
large quantities of Cyanamid with acid phosphate. 

In America, phosphates are sold on the basis of their con- 
tent of phosphoric acid soluble in ammonium citrate solution 
of standard strength, since it has been shown that there is no 
appreciable difference in the agricultural value of the water- 
soluble and the citrate soluble part of the phosphate. It is to 
the interest of mixers of commercial fertilizers to prevent the 
neutralization of the acid phosphate beyond the di-calcium 
or citrate soluble stage. With increasing quantities of CaO 
the following reactions should take place successively, but 
with relatively decreased velocity: 

(a) H 6 P 2 8 + CaO — CaH 4 P.A + H,0, 
Phos. Acid. Water Sol. 

(b) CaH 4 P 2 O s + CaO — Ca 2 H 2 P 2 8 + H 2 0, 
Water Sol. Citrate Sol. 

(c) Ca 2 H 2 P 2 H + CaO — Ca s P 2 8 + H 2 0. 

The last reaction would require a vast excess of CaO, since 
CaoH 2 P 2 8 is practically insoluble in water, and is practically 
undissociated. This reaction does not apply in the practical 
mixing of Cyanamid and acid phosphate. There is, however, 
a further reaction, that may take place with prejudicial results. 

(d) 2Ca 2 H 2 P 3 s + Heat — Ca s P 2 8 + CaH 4 P 2 0„ 
Citrate Sol. Cit. Insol. Water Sol. 

It has been found that with a constant quantity of lime, 



92 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

above a certain minimum, the proportion of citrate insoluble 
phosphate formed is approximately a logarithmic function of 
the temperature. The quantity of Cyanamid that can be safely 
mixed with acid phosphate varies greatly with the nature of the 
acid phosphate, particularly its content of free acid and of 
iron and alumina. For some grades of acid phosphate it may 
be as much as 120 pounds of powdered Cyanamid, for the 
poor grades of acid phosphate as low as 70 pounds of pow- 
dered Cyanamid to 1,000 pounds acid phosphate in a ton 
of complete mixture. 

By the process of granulation, in which the powdered 
Cyanamid is formed into particles which pass through 15-mesh 
and over 50-mesh standard screens, the chemical activity of 
the Cyanamid with acid phosphate is greatly decreased. This 
is mainly due to the fact that the specific surface exposed by 
particles of different sizes varies inversely as their diameters. 
The number of particles per unit of weight varies inversely 
as the cubes of the diameters. One thousand particles one- 
hundredth of an inch in diameter, for instance, would be 
required to make one granule one-tenth of an inch in diameter, 
and the total surface exposed would be one-tenth as much as 
before granulation. Since chemical action can take place only 
on the exposed surface of the solid Cyanamid (the acid phos- 
phate having very little fluidity) it is evident that the localiza- 
tion in a few places of a comparatively large number of widely 
scattered small particles will greatly decrease the amount of 
action that can take place. 

Practically, it has been found that the chemical activity of 
the granulated Cyanamid now being manufactured is 
about one-half the activity of the powdered Cyanamid; 
hence, about twice as much granulated Cyanamid can 
be used in acid phosphate mixtures to produce the same effect 
as a given quantity of powdered Cyanamid. With improve- 
ments in the process of granulation the safe amount will be 
probably further increased. 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 93 

OTHER MIXTURES. 

With other materials commonly used in fertilizer mixtures 
Cyanamid can be mixed in any quantities, without prejudicial 
effect on the valuable constituents. 

ADVANTAGES OF CYANAMID IN FERTILIZER 
MIXTURES. 

Drying Action. — The free acids in acid phosphate are fre- 
quently the cause of dampness and poor mechanical condition 
in mixed fertilizers, causing caking in the bags and making 
the fertilizer difficult of application through drills. To cor- 
rect this undesirable condition it is customary to add to the 
mixture various drying and neutralizing agents. Since the 
particles of Cyanamid are soft and porous and usually con- 
tain less than 1 per cent, moisture they readily absorb free 
moisture from the acid phosphate or other damp materials 
with which they come in contact. More important is the 
action of the lime on the free acids, calcium phosphates tak- 
ing the place of the sticky phosphoric acid, while the heat 
generated by the neutralization aids in dissipating the mois- 
ture uniformly throughout the mixture. This drying action 
is very valuable to the fertilizer compounder. 

Preventing Loss of Nitric Nitrogen. — It has long been known 
by fertilizer manufacturers, and has been demonstrated in 
the laboratory, 1 that when sodium or calcium nitrate is mixed 
with acid phosphate, without the further addition of neu- 
tralizing agents, there is a loss of nitrogen amounting to from 
6 to 10 per cent, of the total nitrate nitrogen added. The 
loss is due to the action of the free acids in the acid phosphate 
upon the nitrate salts. Thus, with sodium nitrate the reaction 
probably is : 

2NaN0 3 + H 3 P0 4 — Na.HPO, + 2HNO,. 

The nitric acid either volatilizes as such or is decomposed to 

nitrogen peroxide and oxygen and escapes from the mixture. 

This loss is prevented by Cyanamid in two ways ; the free 

1 C. S. Cathcart, Jour. Ind. and Eng. Chein., Vol. 3, No. 1, 191 1. 



94 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

phosphoric acid is neutralized by the lime of the Cyanamid, 
and again, the free nitric acid or nitrogen peroxide is neu- 
tralized by the Cyanamid lime immediately after its forma- 
tion. Whatever the mechanism, it has been shown by careful 
experiments that Cyanamid prevents this otherwise serious 
loss of nitrate nitrogen. 

Preventing Bag-rotting. — A similar loss of hydrochloric acid 
gas occurs when potassium chloride, or commercial muriate 
of potash, is mixed with acid phosphate : 

2KCI + H 3 P0 4 — K,HP0 4 + 2HCI. 
This loss does not decrease the commercial value of the 
mixture, but the passage of the acid gases through the cloth 
of which the bag is made decomposes the bag fiber and causes 
so-called "bag-rotting." This destructive action is prevented 
by the addition of Cyanamid to the mixture, causing the neu- 
tralization of the hydrochloric acid gas, or the phosphoric 
acid producing it. 

To the fertilizer manufacturer, the drying and neutralizing 
properties of Cyanamid are decided advantages, since these 
are not possessed by any other high-grade mineral fertilizer, 
and no extra charge is made for them in the selling price of 
Cyanamid. Since the cost of drying and neutralizing agents 
and the extra mixing expense is saved if the nitrogenous 
ingredient possesses these properties, Cyanamid has been 
received with much favor by fertilizer manufacturers. Prac- 
tically the entire output of the American Cyanamid Company 
is sold in this way. 



CHAPTER XI. 



Permanganate Availability of Cyanamid. 



In order to have a ready means of determining the agricul- 
tural availability of the nitrogen in various organic compounds, 
certain chemical methods have been adopted that approxi- 
mately measure this property. The permanganate availability 
methods are in general use for this purpose. It is generally 
assumed that nitrogen compounds soluble in water are readily 
utilized as plant food, but it is also recognized that nitrogen 
compounds insoluble in water may be utilized by the plant in 
the course of growth. It seems to be generally true of organic 
nitrogenous compounds that the solubility in water, together 
with the relative ease with which the insoluble parts are de- 
composed by potassium permanganate bears a regular relation 
to the agricultural availability of the fertilizer. It is interest- 
ing to examine whether Cyanamid takes its proper place in the 
permanganate availability series of values as compared with its 
agricultural availability, and which of the permanganate 
methods gives the truest results. 

The following experiments on the solubility of Cyanamid 
nitrogen in water, and its behavior under the influence of 
potassium permanganate, were made under the direction of the 
author in October, 1912. The Cyanamid used was a low 
grade, granulated material analysing as follows : 

Nitrogen 13.58 per cent. 

Lime (CaO) 50.57 

Moisture • 1 .83 " 

Carbon dioxide 4.00 " 

Size of granules 15 to 50 mesh 

EXPERIMENT I. 

Solubility on Filter. — Samples of 1 gram, 2 grams, 4 grams 
and 8 grams of granulated Cyanamid were placed on filter 
papers and washed with successive portions of distilled water 
at 25 C. until the volume of filtrate reached 250 cc. The 



g6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

nitrogen content of each nitrate was determined with the fol- 
lowing results : 

Sample Grams of Grams of Per cent, of 

grams N. in sample N. in filtrate total N. in filtrate 

J O.1358 O.1227 90.4 

2 0.2716 0.2357 86.8 

4 0.5432 0.4729 87.1 

S 1.0864 0.8x03 74.6 

EXPERIMENT II. 

Solubility in Flasks. — Samples of 2, 4, 8, 17 and 32 grams 
of granulated Cyanamid were placed in Erlenmeyer flasks and 
each covered with 400 cc. of distilled water at 25 C. The 
flasks were stoppered, and allowed to stand 24 hours, with 
occasional shaking. They were filtered through dry niters 
without washing and nitrogen was determined in each filtrate, 
with the following results : 

Sample Grams of Grams of Percent, of 

grams N. in sample N. in filtrate total N. in fillrate 

2 O.2716 O.2548 93.9 

4 O.5432 O.5102 93.9 

8 I.0864 I. OI 19 93.I 

16 2.1728 2.0087 92.5 

32 4-3456 3-9588 91. 1 

EXPERIMENT HI. 
Rate of Solution in Flasks. — In each of five flasks was placed 
2 grams of granulated Cyanamid and 250 cc. distilled water at 
25 C. Each flask was shaken for 10 minutes continuously, 
after addition of the sample, and then only occasionally. After 
filtration without washing, nitrogen was determined in the 
filtrate. The following results were obtained : 

Gram of Gram of Per cent, of 

Time N. in sample N. in filtrate total N. dissolved 

10 minutes 0.2716 0.2055 75-6 

30 " 0.2716 0.2298 84.6 

2 hours 0.2716 0.2403 88.5 

6 " 0.2716 0.2433 89.6 

24 " 0.2716 0.2480 91.3 

Neutral Permanganate Method. — One of the permanganate 
availability methods formerly much used is the neutral 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 97 

permanganate method described in Bureau of Chemistry, U. 
S. Department of Agriculture, Bulletin 107, page 10. In this 
method a sample of fertilizer containing about 0.075 grams of 
nitrogen is digested for 30 minutes on a water or steam bath 
with 125 cc. of potassium permanganate solution containing 2 
grams of potassium permanganate. It is then diluted with 
100 cc. cold water and filtered and washed until the total filtrate 
amounts to 400 cc. The nitrogen is determined in the residue ; 
the percentage of nitrogen removed is called the availability. 
To obtain the effect of the potassium permanganate this 
method was used, first, with 125 cc. of distilled water in place 
of the permanganate, and second, with the 125 cc. of perman- 
ganate solution. 

Per cent. 

Availability with water in place of permanganate 94-34 

Availability with permanganate 87.54 

Since the only difference in the above experiments was the 
absence of the 2 grams of potassium permanganate in the first 
run, it is evident that potassium permanganate has the effect 
of converting about 7 per cent, of the total nitrogen into in- 
soluble compounds. 

Alkaline Permanganate Method. — In this method the avail- 
ability is measured by the amount of ammonia that is formed 
and distilled from an alkaline permanganate solution. An 
amount of sample containing 0.045 grams of nitrogen is 
digested below the boiling point with 100 cc. of solution con- 
taining 15 grams of sodium hydroxide and 1.6 grams of 
potassium permanganate, for thirty minutes. It is then boiled 
and the distillate collected until 85 cc. is obtained. The per- 
centage of nitrogen distilled over as ammonia represents the 
availability. In order to learn the effect of each reagent a run 
was made by this method using, first, 100 cc. of distilled water 
in place of the alkaline permanganate solution; second, a run 
was made with 15 grams of sodium hydroxide in 100 cc. of 
solution, and a third run was made with both sodium hydroxide 
and potassium permanganate in 100 cc. solution. The results 
were as follows : 



98 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

Per cent. 

Availability with water alone 13-79 

Availability with water and sodium hydroxide 53-9° 

Availability with water and sodium hydroxide and 

potassium permanganate 4.75 

This experiment shows that the nitrogen in Cyanamid is only 
slowly converted into ammonia by the action of boiling water 
alone, and that it is much more rapidly converted into ammonia 
in the presence of sodium hydroxide. By the action 
of potassium permanganate, however, the formation of 
ammonia is almost completely prevented, even in the presence 
of sodium hydroxide. 

Hence, in the above methods the addition of potassium per- 
manganate has the opposite effect from what was intended to 
be the function of potassium permanganate, namely to make 
insoluble compounds soluble and to convert complex com- 
pounds to the ammonia form. In the case of Cyanamid, the 
neutral permanganate method makes some water-soluble com- 
pounds insoluble, and the alkaline permanganate method practi- 
cally prevents the formation of any ammonia. 

The method which is lately coming into favor is the modified 
alkaline permanganate method adopted by the Agricultural 
Experiment Stations of New York, New Jersey and the New 
England States on March 4, 191 1. 

Modified Alkaline Permanganate Method. — This differs from 
the other methods in that an amount of sample equivalent to 
0.050 grams of nitrogen is first washed on a filter with distilled 
water at room temperature until 250 cc. of filtrate is obtained. 
This is intended to remove all the water-soluble nitrogen. As 
a matter of fact, it removes about 87 per cent, out of a possible 
94 per cent, of water soluble nitrogen in a low-grade Cyanamid, 
■jv.d about 89 per cent, out of a possible 96 per cent, in a high- 
grade Cyanamid. The "insoluble" residue is digested for thirty 
minutes in a flask with 120 cc. of solution containing 2.5 grams 
potassium permanganate and 1.5 grams sodium hydroxide, and 
the ammonia is then distilled by boiling until 95 cc. of distillate 
is obtained. The sum of the percentage of water soluble nitro- 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 99 

gen and of nitrogen in the distillate represents the availability. 
By this method the sample used in these experiments gave 
90.20 per cent, availability. 

C. S. Cathcart, State Chemist at the New Jersey Agricultural 
Experiment Station, made some experiments with samples of 
powdered Cyanamid, using the regular modified alkaline per- 
mangate method, with the following results. 

Sample number 2S4 2S5 294 295 30S 

Per cent. Per cent. Per cent. Per cent. Per cent. 

Qualitative test for nitrates, none none none none none 

Total nitrogen. 15-76 1357 13-29 14.00 16.40 

Nitrate and a mm o n i a c a 1 

(Ulsch-Street) 6.98 5.53 3.50 4.72 7.32 

Ammonia salts (magnesia) - - 0.92 0.57 0.45 0.55 0.91 

Water soluble (total) 14-15 U-93 12.23 12.88 14-67 

Water insoluble 1.25 1.64 1.06 1. 12 1.73 

Active insoluble (distilled 
from alkaline permanga- 
nate) 0.17 0.17 0.25 0.32 0.33 

Inactive insoluble 1.08 1.47 0.81 0.80 1.40 

Total nitrogen as water solu- 
ble and active insoluble. 93.1 89. 2 93.4 94.3 91.5 

It is interesting to note that as much as 40 per cent, of the 
Cyanamid nitrogen is converted to ammonia by the reducing 
action of the iron and sulphuric acid used in the Ulsch-Street 
method. 1 The amount of ammoniacal nitrogen originally pre- 
sent is shown by magnesia distillation to be from 3 to 6 per 
cent, of the total nitrogen. The qualitative test showed no 
nitrates present. 

The water-soluble nitrogen with one washing of 250 cc. 
distilled water is from 87 to 92 per cent, of the total, the 
average being 90.6 per cent. By treatment with alkaline per- 
manganate the available nitrogen is found to be 92.5 per cent. 
as an average of the five samples. 

In order to determine the effect of a more thorough initial 
washing, Cathcart repeated the availability experiments wash- 
1 For Ulsch-Street Method see U. S. Dept. of Agr. Bureau of Chem., 
Bui. 107., or Wiley's Principles and Practice of Agricultural Analy- 
sis, Vol. 1, p. 445. 



28 4 

'er cent. 


285 
Per cent. 


294 
Per cent. 


295 
Per cent. 


30S 
Per cent. 


15-76 


13-57 


13-29 


14.00 


16.40 


14.71 


12.13 


II.89 


12.78 


14.50 


0.08 


O.32 


O.32 


0.32 


O.49 


O.I2 


O.I2 


O.I2 


0.08 


0-33 


14.91 


12.57 


12.32 


13.18 


15-32 


0.14 


O.22 


O.23 


0.22 


0.31 


0.71 


O.78 


0-73 


0.60 


0.77 



IOO CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

ing each sample three times with 250 cc. water each time. The 
following results were obtained : 

Sample number 

Total nitrogen 

Soluble nitrogen, 1st 250 cc. 
" " 2nd " . 

3rd " . 
Total soluble nitrogen .... 
Active insoluble nitrogen. 
Inactive " " 

Total nitrogen as water sol- 
uble and active insoluble 95.5 94.3 94.5 95.7 95.3 

It is seen that with this change in the procedure the water- 
soluble nitrogen averages 93.5 per cent, and the total available 
95.1 per cent. 

The percentage of available nitrogen revealed by the 
modified alkaline permanganate method is practically a ques- 
tion of the solubility and the rate of solution of Cyanamid 
nitrogen in the initial washing with distilled water. The in- 
fluence of size of sample and of rate of solution is shown in 
the preliminary experiments on page 96. It is evident that to 
determine the true amount of water-soluble nitrogen in 
Cyanamid by the modified alkaline permanganate method a 
longer period of contact should be allowed between sample 
and solvent in the initial washing, or more solvent should be 
used. The simplest way would be to let the sample stand in a 
flask with distilled water for 24 hours and filter, or to agitate 
on a shaking machine for about three hours. 

Whether or not the availability determined by the perman- 
ganate methods corresponds with the fertilizer efficiency of 
Cyanamid is a question principally of determining what the 
fertilizing efficiency is, since the permanganate methods are 
easily carried out in the laboratory. The concensus of opinion 
seems to be that Cyanamid has about the fertilizing value of 
sulphate of ammonia, and this is about 95 per cent, of the 
efficiency of nitrate of soda, as an average of all kinds of 
conditions, favorable and unfavorable, that might occur in 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 101 

agricultural practice. Both sulphate of ammonia and nitrate 
of soda, however, show an availability of ioo per cent, by the 
permanganate methods, while Cyanamid shows about 87 to 89 
per cent, by the neutral permanganate method, 4 to 8 per cent, 
by the alkaline permanganate method, 90 to 94 per cent, by the 
modified alkaline permangante method, and 94 to 96 per cent, 
by simple solution in water for 24 hours. The neutral and the 
modified alkaline methods therefore approximate to a certain 
extent the values that they should represent, the straight 
alkaline method is wholly unsuitable, while the simple solution 
in water gives the most significant results. 



CHAPTER XII. 



Fire and Water Hazard of Cyanamid. 



The combustibility of Cyanamid and its susceptibility to 
damage by fire and water have been thoroughly investigated 
by the Underwriters' Laboratories of Chicago, 111. The fol- 
lowing results were obtained through the courtesy of Mr. 
A. H. Nuckolls, Chemical Engineer, of the Underwriters' 
Laboratories, and are a part of the report prepared for the 
information of fire insurance companies : 

"The object of the investigation was to determine the nature 
of recommendations to be made relative to issuance of an 
opinion upon the fire hazard of the product. This report 
does not deal with the hazards of mixtures of this product 
with other fertilizers." 

"Test for Flammable Gases. — Tests for flammable gases were 
conducted by placing about 5 pounds of the product in a 
large bottle, about 6 inches internal diameter by 16 inches in 
height, and adding an excess of water. The bottle was pro- 
vided with a loose fitting stopper to which wires were attached 
for producing an electric spark inside of the bottle. The 
spark was produced at intervals of about 15 minutes at the 
beginning of the test. The bottle was allowed to stand for 
10 days, the spark being produced about every 3 to 4 hours 
except during the night. The test was repeated employing 
a gas testing flame instead of the electric spark and also 
varying the proportions of gas and air. 

"No analysis of the gas evolved was conducted. . . . 
Mixtures of air with gases evolved when test samples were 
treated with water did not ignite or burn when brought into 
contact with electric spark and gas flame." 

"Spontaneous Heating Tests. — Acceleration Test. — This test 
was conducted by means of an apparatus consisting essentially 
of a wire gauze cylinder about i J / 2 inches in diameter and 
6 inches long, which is surrounded by a double- jacketed 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES 103 

copper water-bath provided with a tight fitting top or lid, 
a thermometer and inlet and outlet tubes to admit air. The 
sample was placed in the wire gauze cylinder, and the ther- 
mometer inserted so that its bulb was within the sample near 
its center. The temperature of the bath was maintained at 
ioo° C. for 4 weeks. For the first 6 hours of the test, tem- 
perature readings were taken every half hour. Afterwards, 
readings were taken twice daily until the test was concluded. 
"The thermometer showed that the internal temperature of 
the sample remained at approximately ioo° C. during the 
tests." 

"Test with Water. — About 10 pounds of the product were 
placed in a wooden cylinder, approximately 10 inches in height, 
and 10 inches internal diameter, the walls of the cylinder 
being about 1 inch in thickness. The temperature of the 
sample was allowed to become the same as that of the room, 
and then about 4 pounds of water, the temperature of which 
was observed, were added with stirring. The mixture was 
then allowed to stand and its temperature observed for a 
period of about a week. 

Test started at 10.30 A. M. Degrees C. 

Temperature of room during test, about 18 

" " water at start 18 

'• " test sample of product at start 17 

" " mixture at 11.00 A. M., about 20 

"No material rise in the temperature of the mixture was 
observed." 

"Acid Tests. — One pound samples of the product were 
treated with concentrated hydrochloric, sulphuric, and nitric 
acids and the results observed. 

"The acids reacted readily with the samples with consid- 
erable evolution of heat, compounds of these acids and lime 
being produced, and the Cyanamid (CaCN 2 ) was also attacked 
and decomposed. No combustion or explosive action took 
place." 



104 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

"Behavior of Product when Heated. — Two 20-gram test 
samples were heated in a large porcelain dish by means of a 
Bunsen burner. The heat was gradually increased until the 
temperature of the samples was above a bright red heat. 
During the test a small gas-testing flame was constantly 
applied to the samples. 

"At the start oil vapors were given off but not in sufficient 
quantity to form a flame. The samples were decomposed 
but no material amount of combustion occurred." 

"Test with the Oil Used. — A sample of oil employed in the 
manufacture of Cyanamid was obtained directly from the 
manufacturer. Small samples of the oil were also obtained 
from the product by extraction with petroleum ether. 

"Specific Gravity. — Specific gravity was obtained roughly 
by means of a Be. hydrometer. The specific gravity was 
found to be approximately 30 Be. at 19 C. 

"Flashing Point. — The flashing point was determined with 
the Pensky-Martens tester, the standard method of test with 
this apparatus being followed. The flashing point was found 
to be 150 C. (221 F.) closed cup. 

"Evaporation. — An evaporation test was conducted by heat- 
ing about ]/ 2 gram of a sample of the soil, spread out on a 
watch-glass, for 5 hours at ioo° C. in an ordinary oven and 
determining the loss of weight of the sample. The loss by 
evaporation was found to be 1.1 per cent, by weight in 4 
hours. 

"Spontaneous Heating. — This test was conducted by heating 
14 grams of the oil, disseminated over 7 grams of cotton, at 
a temperature of ioo° C. for 48 hours in an apparatus con- 
sisting essentially of a wire gauze cylinder, about \ l / 2 inches 
in diameter and 6 inches long, surrounded by a double-jacketed 
copper water-bath provided with a tight fitting top, thermom- 
eter, inlet and outlet tubes to admit air. The oiled cotton was 
placed in the wire gauze cylinder, and the thermometer in- 



CYANAMID — MANUFACTURE, CHEMISTRY AND USES I05 

serted so that its bulb was within and near the center of the 
oiled cotton. Observations were made to note if any differ- 
ence between the temperature of the sample and the water- 
bath occurred. 

"The internal temperature of the test sample remained 
slightly below ioo° C. during the first 5 hours of heating, and 
never exceeded ioo° C. the temperature of the surrounding 
bath." 

"General Behavior when Treated with Water. — A stream of 
water at about 75 pounds pressure from a l / 2 inch nozzle was 
applied to a bag for 15 minutes, the stream being directed so as 
to wet the entire external surface of the bag. The bag was 
then allowed to stand about a week, and an average sample was 
analyzed according to the method of Gunning. 

"The sample did not readily absorb water, owing to the 
presence of oil which retarded immediate contact of the water 
with the lime-nitrogen compound. Water was, however, 
gradually absorbed with a very slow evolution of gas in small 
quantity. A marked odor of ammonia was noted. When 
allowed to dry in air, the sample hardened to some extent, or 
in other words 'caked.' This 'caking' was in a measure due to 
absorption of carbon dioxide from the air. 

Per cent. 

Nitrogen in sample before wetting 1444 

Nitrogen in sample after wetting 13. 10 

Apparent loss of nitrogen 1 .34 

The following conclusions were drawn with regard to the 
fire and water hazard of Cyanamid : 

"It is readily decomposed by high temperatures, and also by 
mineral acids which attack it somewhat violently with the 
evolution of considerable heat. Its decomposition by water is 
not accompanied by a material rise in temperature or the 
formation of hazardous products in dangerous quantity. It is 
not liable to spontaneous ignition. 

"The product is non-flammable, and is not combustible to 



106 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 

a material extent. The product is decomposed by high tem- 
peratures such as are produced in burning buildings. It will 
be noted that a relatively small amount of oil (4.2 per cent.) 
and carbon 13.25 per cent.) are present. The high tempera- 
ture to which the free carbon is subjected in the electric 
furnace renders it sufficiently graphitic to be difficulty com- 
bustible. 

"The product is susceptible to damage to a material extent 
by fire or water. The product does not readily take up water, 
and is not a good conductor of heat. In case of fire it will, 
therefore, probably be only partially damaged by the heat and 
water. 

"The product is considered non-hazardous except in respect 
to susceptibility to damage by fire and water." 

In the process of manufacture, the cans containing the crude 
calcium cyanamide are withdrawn from the nitrifying ovens at 
a temperature of more than i,ooo° C, and are allowed to cool 
in the open air, without noticeable injury to the calcium 
cyanamide. 



INDEX 



Absorption of cyanamide in soil, 
39-42, 60. 

Acetic acid, action on cyana- 
mide, 12. 

Acetylene, 73. 

Acid fish, in Cyanamid fertilizer 
mixtures, 90. 

Acid phosphate, mixtures with 
Cyanamid, 91-94. 

Acids, action on cyanamide, 12, 13, 
103, 104, 106. 

Acid soils, fertilizers on, 70, 74, 83. 

Activity of Cyanamid with potas- 
sium permanganate, 95-101. 

Addition compounds of cyana- 
mide, 13. 

Aeration, influence on cyanamide 
conversion, 47. 

Air, effect on cyanamide decom- 
position, 47. 

Alkaline permanganate method, 
97-101. 

Aluminium hydroxide, effect on 
cyanamide decomposition, 52, 
53, 54- 

American Cyanamid Co., capacity 
of factories, 3. 

Amidodicyanic acid, 15 ; identi- 
fication of, 23. 

Ammelide, 12. 

Ammeline, 12 ; identification, 23. 

Ammonia from Cyanamid, 8, 12 ; 
loss in storage, 24-31. 

Ammonia, loss of in fertilizer mix- 
tures, 90. 

Ammonium compounds, formation 
in cyanamide decomposition, 45, 
46. 

Ammonium salts in Cyanamid fer- 
tilizer mixtures, 90. 



Ammonium sulphate, excessive ap- 
plications, 69 ; use in Cyanamid 
mixtures, 90. 

Analysis of typical Cyanamid, 8. 

Analysis— see analytical methods. 

Analytical methods : total nitro- 
gen, 19, 20 ; cyanamide, nitro- 
gen, 20-22 ; dicyandiamide nitro- 
gen, 20-22 ; amidodicyanic acid, 
23 ; ammeline, 23. 

Application of excessive quantities 
of Cyanamid, 69-S4 ; normal 
quantities, 73, 87, 89. 

Ashby, 36. 

Aso, K, 77, 78. 

Availability of Cyanamid — perman- 
ganate methods, 95-101. 

Available phosphoric acid, in 
Cyanamid mixtures, 91-92. 

Bacteria — effect on decomposition 
of cyanamide, 32-36 ; not neces- 
sary in decomposition of cyana- 
mide to urea, 40, 43, 44, 45, 50, 
56, 58, 59- 

Bags, storage of Cyanamid in, 25. 

Bag-rotting, prevention of, 94. 

Barium carbide, 2. 

Barium cyanamide, 2. 

Bases, action on cyanamide, 12, 13. 

Basic calcium cyanamide, 16. 

Bauxite, effect on cyanamide de- 
composition, 52, 53. 

Behrens, 36. 

Bineau, 10. 

Brioux, Ch. Decomposition pro- 
ducts in exposed Cyanamid, 29, 
30 ; modified Caro method for 
analysis of cyanamide and di- 
cyandiamide, 21 ; pot tests, 77. 

Bun sen, 1. 

Calciocianamide, definition, 4. 

Calcium acid cyanamide, 14. 



ioS 



INDEX 



Calcium — effect on decomposition 
of cyanamide in soil, 33. 

Calcium carbide, analysis, 6 ; effect 
of in fertilizer, 73 ; manufacture 
of, 2, 4. 

Calcium Cyanamid, definition of, 4. 

Calcium cyanamide, definition of, 
4 ; formation, 2 ; properties, 14 ; 
temperature of formation, 2 ; 
volatility, 6. See also Cyanamid. 

Calcium cyanamide carbonate, 16, 
17, 38. 

Calcium cyanamide, definition, 4. 
See also calcium cyanamide and 
Cyanamid. 

Calcium hydroxide, effect on cyana- 
mide decomposition, 48. See al- 
so calcium, lime. 

Calcium nitrate, excessive appli- 
cations, 69. 

Carbide. See calcium carbide, ba- 
rium carbide. 

Carbon, effect on cyanamide de- 
composition, 50. 

Carbon dioxide, action on calcium 
cyanamide, 16 ; action in soil, 
37, 38 ; effect on Cyanamid in 
storage, 24-28. 

Cannizzare, 10. 

Caro, Dr. Nicodem, 1, 2, 6, 11, 17; 
method of analysis, 20. 

Catalytic agents, in cyanamide de" 
composition, 42, 48-56, 5S. 

Cementing powders, 9. 

Cereal crops, 86. 

Chloroform — as sterilizing agent, 
33. 57- 

Cladosporium, in decomposition of 
cyanamide, 34-36. 

Climate, effect on Cyanamid in 
storage, 24-31. 

Cloez, 10. 

Colloids — effect on cyanamide de- 
composition, 48-59. 

Commercial Cyanamid. See Cyana- 
mid. 
Commercial derivatives, 8. 



Complete fertilizer mixtures, 89-94. 

Conversion of available phosphoric 
acid in Cyanamid mixtures, 91-92. 

Copper oxide process, 5. 

Concentration of cyanamide, effect 
on decomposition, 40, 42, 46, 47. 

Cyanamid: Agricultural use, 83-89; 
analysis, 7, S ; analytical meth- 
ods, 19-22 ; availability, 95-101 ; 
decomposition in soil, 32-59; de- 
finition of term, 4 ; derivatives, 
S-18 ; development of industry, 
1-8; excessive applications, 69; 
fertilizer mixtures, 90-94 ; fire 
and water hazard, 102-106; manu- 
facture, 4-7 ; nitrification, 62-64 \ 
retention in soil, 60-61 ; solu- 
bility, 95-96; storage, 24-31; 
toxicity, 65-82. See also cyana- 
mide. 

Cyanamide: Action of acids, 12; 
alkalies, 12; heat, 11; oxidizing 
and reducing agents, 13, 95-101 ; 
analysis of, 19-21 ; decomposition 
in soil, 32-59 ; definition of term, 
4; derivatives, 13-17; discovery, 
10; properties, 11. See also 
Cyanamid. 

Cyanides : Absent in Cyanamid, 2, 
8 ; manufacture, 8 ; part in de- 
velopment of Cyanamid indus- 
try, 1. 

Cyanuric acid, 12. 

Decomposition of Cyanamid in soil, 
32-59 ; effect of — aeration, 47 ; 
aluminum hydroxide, 52-54 ; 
bauxite, 52-53 ; colloids, 48-59 ; 
concentration of solution, 40, 
carbon, 50; electrolytes, 48; 
glass sand, 52-54 ; heat, 43 ; iron 
oxide, 52-54, 56; iron hydrox- 
ide, 54, 55 ; kaolin, 52-53 ; silicic 
acid, 54 ; soil, 32-49 ; sterile soil, 
44. 5°. 56; umber, 52 ; tempera- 
ture, 43 ; zeolites, 49; products 
formed, 43-45, 51 ; stages in, 37, 
38, 57- 



INDEX 



IO9 



Decomposition of Cyanamid in stor- 
age, 28, 29. 

Definitions of terms used in Cyan- 
amid industry, 3-4. 

Derivatives of Cyanamid, 8-18. 

Di-calcium phosphate in Cyanamid 
mixtures, 91-92. 

Dicyaudiamide ; commercial pro- 
duction, 9; conversion in soil, 77; 
decomposition, 75, 76; formation 
in Cyanamid, n, 43,44, 51, 75; 
method of treating subject, 74; 
properties, 17, 18; pure versus 
impure, 77-82 ; toxicity, 77-82. 

Dicyandiamidine, analysis, 21 ; 
properties, iS. 

Dimetal salts of cyanamide, 13. 

Discovery of Cyanamid, 1. 

Drying action of Cyanamid in fer- 
tilizer mixtures, 93. 

Duration of Cyanamid nitrogen in 
soil, 64. 

Dye industry, use of/licyandiamide 
in, 9. 

Efficiency of utilization of nitrogen 

in fertilizers, 69, 84. 
Electric furnace, 1, 4. 
Electrolytes, effect on cyanamide 

decomposition, 47. 

Equilibrium, temperature, 6 ; pres- 
sure, 6. 

Errors in fertilizer experiments, 84, 
85- 

Excessive applications, effect of, 
69, 72, 82, 84. 

Experimenting with fertilizers, 69, 
83-86. 

Explosives, Cyanamid derivatives 
for use in, 9. 

Exposure of Cyanamid, effect of, 

25-31- 
Factory storage of Cyanamid, 24. 
Ferrodur, 9. 



Fertilizer : excessive application of, 
69-73, 84 ; mixtures with Cyana- 
mid, 89-94; preparation of Cyana- 
mid as material for, 7 ; use of 
Cyanamid as, 73, 87, 89. 

Fineness of Cyanamid, 7. 

Fire and water hazard of Cyanamid, 
102-106. 

First stage of decomposition of cal- 
cium cyanamide, 37, 38. 

Florida, storage test in, 24, 31. 

Frank, Dr. Albert R., 3, 85. 

Frank, Prof. Adolph, 1. 

Freudenberg, Herman, 3. 

Fungi —in decomposition of cyana- 
mide, 35, 36. 

Germination, effect of Cyanamid 
on, 82. 

Glass sand, effect on cyanamide 
decomposition, 52, 53, 54. 

Glucose — effect in decomposition of 
cyanamide, 34-36. 

Granulated Cyanamid, 7 ; activity 
compared with that of powdered 
Cyanamid, 92, availability of, 
96-99; solubility of, 95-96. 

Guanidine, 9. 

Gunning method in Cyanamid an- 
alysis, 19. 

Hall, A. D., 60. 

Haloid acids, 12. 

Hardening powders, 9. 

Haselhoff, E., 73. 

Hazard, fire and water, of Cyana- 
mid, 102-106. 

Headden, 72. 

Heat, effect of on Cyanamid, 102- 
106. 

Heat, effect on conversion of dical- 
cium to tricalcium phosphate 
91, 92. 

Heating soil, effect on cyanamide 
decomposition, 49. 

Henschel, G., 11, 22 — decomposi- 
tion products in exposed Cyana- 
mid, 30, 31. 



no 



INDEX 



History of Cyanamid industry, I. 

Hutchinson, 61. 

Hydrogen, effect on cyanamide 
conversion, 47. 

Hydrogen sulphide, action on cyan- 
amide, 12. 

Hydrolysis of cyanamide salts, 14. 

Increase in weight during storage, 

24-31. §5- 

Intensit, 9. 

Inouye, R., 77, 78. 

Iron hydroxide, effect on cyana- 
mide decomposition, 54, 55. 

Iron ore, effect on cyanamide de- 
composition, 52, 53, 54. 

Iron oxide, effect on cyanamide de- 
composition, 52, 53. 

Jacksonville, Fla., storage test at, 

24, 3i- 

Jacob}', 10. 

Kalkstickstoff, definition, 4. 

Kaolin, effect on cyanamide de- 
composition. 52, 53. 

Kappen, H., 32 ; experiments with 
soil, 34 ; experiments with col- 
loidal substances, 51-59; effect of 
acetylene, 73; value of dicyandia- 
mide, 77. 

Kjeldahl method, suitable for 
Cyanamid nitrogen determina- 
tion, 19. 

Kloppel, J., 86. 

Large applications of fertilizer, 69, 
72. 

Laterite earth, effect on cyanamide 
decomposition, 52, 53. 

Liberi, G., 76. 

Lime, action on cyanamide, 13, 36. 
See also Calcium, calcium hy- 
droxide. 

Lime-nitrogen, definition, 3. 

Liquid air, source of nitrogen, 5. 

Lohnis, 77. 

Manganese dioxide, effect on cyan- 
amide decomposition, 52, 53. 



Manganese hydroxide, effect on 
cyanamide decomposition, 54. 

Mehner, Prof. H., 1. 

Melamine, 12, 15. 

Mellon, 12. 

Metallurgy, use of Cyanamid in, 9. 

Methylamine from cyanamide, 13. 

Miller, N. H. J., 61. 

Milo, C. J., 77, So, 81. 

Mixed fertilizers, Cyanamid in, 
89-94. 

Modified alkaline, permanganate 
method, 98-101. 

Moissan, 1. 

Moisture, effect on Cyanamid in 
storage, 24-31. 

Moor soils, fertilizers on, 70, 74. 

Miintz, 63, 86, 

Mustard, destruction with lime- 
nitrogen in oat fields, 86. 

Neutralizing properties of Cyana- 
mid, 91-94. 

Neutral permanganate method, 96- 
101. 

Niagara Falls, Ontario, storage 
test at, 25-27. 

Nitrate nitrogen — preventing loss 
by use of Cyanamid, 93. 

Nitrates, effect on analysis of Cyan- 
amid, 19 ; effect on cyanamide 
decomposition, 48. 

Nitric acid, action on cyanamide, 
12 ; effect on cyanamide decom- 
position, 48; manufacture from 
lime-nitrogen, 8 ; preventing loss 
of in fertilizer mixtures, 93, 94. 

Nitrification, in acid soils, 83 ; of 
Cyanamid compared with am- 
monium sulphate, dried blood, 
etc., 62-64. 

Nitrites, action on cyanamide, 13. 

Nutritive substances, effect of pres- 
ence in cyanamide decomposi- 
tion, 32-36, Si. 



INDEX 



I I I 



Nitrogen, analysis of in Cyanamid, 
19, 20 ; duration of Cyanamid in 
soil, 64 ; excessive applications 
of, 69-73; fixation of as Cyanamid, 
1-8 ; prevention of loss as nitrate 
nitrogen, 93. 

Nitro-guanidine, 9. 

Nitrolim, definition, 4. 

Nomenclature, 3. 

Nottin, 63, 86. 

Nuckolls, A. H., 102. 

Oat-fields- destruction of wild mus- 
tard in, 86. 

Oats, excessive applications of ni- 
trogen on, 69. 

Oil in Cyanamid, 7, 104. 

Old Cyanamid, compounds in, 28. 

Ostwald Process, 8. 

Oxidizing agents, action on cyana- 
mide, 13. 

Patents, Cyanamide, 3. 

Penicillum brevicaule, in decom- 
position of cyanamide, 35, 36. 

Permanganate ; potassium — effect 
on Cyanamid, 95-101. 

Perotti, 77. 

Phosphates -mixtures with Cyana- 
mid, 91-94. 

Phosphoric acid, action on cyana- 
mide, 12. 

Play fair, I. 

Poison, definition of, 65. 

Potassium hydroxide, effect on 
cyanamide decomposition, 48. 
See also alkalies. 

Potassium permanganate, effect on 
Cyanamid, 95-101. 

Power consumption, in Cyanamid 
manufacture, 7. 

Preparation of cyanamide, 10. 

Pressure of nitrogen in Cyanamid 
formation, 6. 

Properties of cyanamide, 10-18. 

Pure substances and toxicity, 80. 



Quantity of Cyanamid to apply as 
fertilizer, 88. 

Rate of removal of cyanamide from 
soil solution, 39. 

Reducing agents, action on cyana- 
mide, 13, 99. 

Reis, 36. 

Retention of Cyanamid nitrogen in 
soil, 60. 

Reversion in acid phosphate — 
Cyanamid mixtures, 91. 

Root crops, 86. 

Rothe, F., 2. 

Sabaschnikoff, 77, 80. 

Sackett, 72. 

Sand, effect on cyanamide decom- 
position, 52, 53. 

Schiick, 10. 

Schneidewind, 86. 

Second and third stages of Cyana- 
mid decomposition in soil 38. 

"Secondary products," effect on 
cyanamide decomposition, 33, 
34, 81. 

Sidgwick, 11. 

Siemens & Halske, 1. 

Silicates, effect on cyanamide de- 
composition, 49, 50. 

Silicic acid, effect on cyanamide 
decomposition, 54. 

Silver cyanamide, 17. 

Sodium acid cyanamide, 13. 

Sodium cyanamide, 10, 13. 

Sodium nitrate, excessive applica- 
tions, 69. 

Soil, decomposition of Cyanamid 

in- 3 2 -59- 

Soil solution, rate of removal of 
cyanamide from, 39. 

Sol, iron oxide, effect on cyana- 
mide decomposition, 56. 

Solubility of Cyanamid, 95-101. 

Solution of cyanamide, changes in, 
14, 15, 16, 76; rate of solution of 
Cyanamid, 96. 

Steglich, S6. 



112 



INDEX 



Sterile conditions and cyanamide 
decomposition, 33, 40, 43, 44, 50, 

51, 56, 57- 
Sterilization of soil, effect on cyana- 
mide decomposition, 44, 50, 56, 

57- 

Stickstoffkalk, definition, 4. 

Storage of Cyanamid, variation of 
nitrogen during, 24-31. 

Strohmer, 85. 

Stutzer, 36. 

Substitution compounds of cyana- 
mide, 13. 

Sugar beets, 85, 86. 

Sulphuric acid, action on cyana- 
mide, 12. 

Summary on cyanamide decom- 
position in soil, 57-59. 

Surrogate, 8. 

Temperature, effect on cyanamid 
decomposition in soil, 43, 44 ; re- 
action temperature, barium cy- 
anamide, 2 ; calcium cyanamide, 
2, 6. 

Tempering powders, 9. 

Thio-urea, 12. 

Top-dressing, use of Cyanamid 
as, 87. 

Toxicity : of cyanamide, 34-36 ; of 
fertilizers, 65-82. 



Tri-calcium phosphate in Cyanamid 
mixtures, 91, 92. 

Tricyantriamide, 12. 

Ulpiani, C, chemistry of cyana- 
mide, 12, 14, 16, 22, 23; decom- 
position of Cyanamid in soil, 
3 2_ 5 r > 57> 59; dicyandiamide, 
34, 77- 

Umber, effect on cyanamide decom- 
position, 52, 53. 

Underwriters' Laboratories, 102-106. 

Urea, assimilation of, 60 ; deter- 
mination of, 22 ; formation from 
cyanamide, 12, 15, 37, 43, 44, 51, 
89 ; manufacture, 9 ; transforma- 
tion by bacteria, 40, 44, 57. 

Volatility of calcium cyanamide, 6. 

Water : Effect on Cyanamid in 
storage, 24-31 ; hazard of in fires, 
103, 105, 106 ; hydrolysis of 
cyanamide salts in, 14 ; solu- 
bility of Cyanamid, 95-101. 

Weeds, destruction with lime-ni- 
trogen, 86, 87. 

Weight, increase during storage of 
Cyanamid, 24-31, 85. 

Wheat, 86. 

Willson, 1. 

Zeolites, effect on cyanamide de- 
composition, 49, 50. 



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